Serban, Trajan’s Bridge Over the Danube

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The International Journal of Nautical Archaeology (2009) 38.2: 331–342doi: 10.1111/j.1095-9270.2008.00216.x

© 2009 The Author. Journal Compilation © 2009 The Nautical Archaeology Society.

Published by Blackwell Publishing Ltd. 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA.

BlackwellPublishingLtdMARKOSERBAN:TRAJAN’SBRIDGEOVERTHEDANUBENAUTICALA RCHAEOLOGY,38.1

Trajan’s Bridge over the Danube

Marko Serban

Institut d’Art et d’Archéologie, Université de Paris 1 Panthéon Sorbonne, 75006 Paris

For the final conquest of Dacia, Apollodorus of Damascus, Trajan’s principal engineer, built a monumental bridge over the

Danube in AD 105. This paper aims at understanding the historical circumstances and environmental conditions during the

building of Trajan’s bridge, as well as its construction technology, by analysing the limited written and iconographic ancient

sources. It also offers an overview of archaeological research on the structure to date, with special attention to the 2003

underwater archaeological survey, which established the state of preservation of the remaining piers, emphasizing the need

for their long-term protection.

© 2009 The Author

Key words:

bridge, Trajan, Danube, piers, multibeam sonar.

R

esearch on Trajan’s Bridge, the remains of which are now located in the artificiallake between the two hydroelectric power

stations, Djerdap I and Djerdap II, on the Danube(Fig. 1), is one of the most ambitious endeavoursof Serbian underwater archaeology. It began in

1979 with the survey and large-scale excavation

of two important Roman sites near Kostol, 5 kmfrom Kladovo. The first was the bridge itself,constructed by Apollodorus of Damascus in 103– 105 AD, and the second was Castellum Pontes,which guarded the bridge on the right (south)bank. These two sites, together with the camp

at Drobeta on the left (north) bank of the

Figure 1. Location map of the Iron Gates. (M. Serban)



NAUTICAL ARCHAEOLOGY, 38

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332 © 2009 The Author. Journal Compilation © 2009 The Nautical Archaeology Society

river, represent in strategic terms one combinedsite.

Professor Milutin Gara

s

anin of BelgradeUniversity conducted several archaeological cam-paigns between 1979 and 1982 as part of rescueexcavations of monuments endangered by the con-

struction of the Djerdap II dam, and publisheda preliminary report for the year 1979, whichserved as a base for further research (Gara

s

aninand Vasi

ç

, 1980). More than 20 years later, in2003, archaeological exploration began onceagain with underwater research, the principal aimbeing to establish the state of preservation of theremaining bridge piers. Multibeam sonar wasused for surveying the 1100-m-long route of thebridge. The long-term objective of the project iscarefully to determine the method of constructionused by Apollodorus of Damascus, and to protectthe remains from devastating natural influences,and from river traffic.

One of the main reasons for studying thismonument is not only the fact that its creator wasconsidered to be the greatest Roman Emperor,

1

but also because it enabled him to conquer Daciaand thus become one of the greatest generals of the Empire. A pontoon built in AD 101 upstreamfrom Laederata, for the purposes of the FirstDacian War, was not sufficient for the finalconquest of that region (Tudor, 1974: 20). Thiswas resolved when Trajan’s bridge was finished inAD 105. The resulting considerable territorial

extension of the Empire to the north-east remainedunder Roman rule for a long time, as opposedto the empire’s expansion to the east.

2

Whilepreserving its military purpose, the bridge couldhave helped develop the economic and culturalexchange which enabled a fast Romanization of that region.

The geographical context

In a broader geographical context, the remains of Trajan’s bridge are situated between the Southern

Carpathians and the Northern Balkan Moun-tains (Fig. 1). Ten remaining piers are located inthe stream-bed of the Danube, exactly 929.7 kmfrom the river-mouth, near the village of Kostol(ancient Castellum Pontes) on the Serbian bankand Drobeta-Turnu Severin on the Romanianbank. The bridge was built at the exit from theIron Gates, one of the biggest river-gorges in theworld, 135 km long, and with a width varyingfrom 2 km at the entrance to the Upper Gorge to150 m in the Lower Gorge. The bridge was built

on the spot where the river was slowing downand widening again (to almost 1 km) and wherethe depth was relatively shallow.

Site topography, the 1979 survey

A large valley on the right (south) bank joins theDanube course near the cutwater pier that standsout, along with two piers of the access ramp andthe portal (Fig. 2), which were in a fairly satis-factory state of preservation. The valley is flankedby two plateaus, whose landforms suggest theexistence of fortifications. The eastern plateau islarger, with a bigger fort, of 112 ×

120 m, accordingto surface observations (Gara

s

anin and Vasi

ç

,1980: 26). It is important to point out that therewas no evidence of towers at the presumed anglesof the construction, except for the north-west one,where an unauthorised excavation uncovered theinterior of a tower. From surface observationsthe fortification on the western plateau, upstreamfrom the bridge, was smaller, 50 ×

30 m (Gara

s

aninand Vasi

ç

, 1980: 26), but the finds on both siteswere the same—Roman and medieval pottery,Roman being predominant on the eastern plateau.

These observations about the presumed shapeof the fort on the eastern plateau and the possibleexistence of a gate in the western wall, allowedarchaeologists to presume the existence of anearly Roman imperial castellum on that spot witha praetorian gate on the north. It is possible to

accept that by its type, regardless of the differentdimensions, this fort is similar to the one built onthe opposite bank, the camp of Drobeta. All of this allowed the identification of this site asCastellum Pontes.

Greater sand sedimentation has been causedby deceleration of the flow after the creation of the dammed lake, and by dredging upstream inthe Kladovo region in the past few years. Thesedimentation layer was not examined on theentire route of the bridge, but in certain places itwas several metres thick. The bottom (a layer of

compacted gravel, studied during the strati-graphic analysis in 1979) is solid beneath the sandand relatively flat. The average depth of the Danubehere was 5 m before the dam was built, and is nowmore than 10 m.

Roman preparations for crossing theDanube

Our principal subject here will be somewhatwidened to explain the arrangements the Romans



M. SERBAN: TRAJAN’S BRIDGE OVER THE DANUBE

© 2009 The Author. Journal Compilation © 2009 The Nautical Archaeology Society 333

had to make before the creation of such a hugebridge. The Danube limes

protected the Empirefrom outer attacks, but the river itself presented agreat obstacle for further expansion. Overcomingthis problem required comprehensive preparationsthat lasted for more than half a century.

The Roman road in the Iron Gates was built in

stages; it was started under Tiberius in AD 33– 34, and finished in the reign of Trajan in AD 101(Jordovic, 1983: 367–8). This road had thehighest strategic importance; not only did it aida natural defensive line in the north of theEmpire, but it also gave the Romans access toDacian territory. The sections of the Roman roadcut into the rock, which spread for 23 km, arestill visible at the entrance to the Upper Gorge.

The Roman channel near Sip, nowadaysprobably entirely destroyed by the rise in water-level, is very important in the history of Roman

navigation in general and of the Iron Gates inparticular. The discoveries made in the LowerGorge in autumn 1969 shed a new light on theconditions of navigation in the Iron Gates at thebeginning of the 2nd century AD (Petrovic, 1970:31). During the building of the power stationDjerdap I, a marble plaque was discovered withthe following inscription, engraved in six lines:

Imp(erator) Caesar Divi Nervae f(ilius)/Nerva TraianusAug(ustus) Germ(anicus)/pont(ifex) max(imus)

trib(unicia) pot(estate) V p(ater) p(atriae) co(n)s(ul)IIII /ob periculum cataractarum/ dérivato fluminetutam Da/ nuvi navigationem fecit

(Emperor CesarNerva son of the divine Nerva, Nerva Trajan, theAugustus, Germanicus, Pontifex Maximus, investedfor the fourth time as Tribune, Father of the Fatherland,Consul for the fourth time, by diverting the river has

contoured dangerous cataracts and made the wholecourse of the Danube navigable).

The inscription appears to have been cut before10 December 101. The cataracts mentioned markthe existence of submerged rocks, rapids andwhirlpools, which are very frequent in this sectorof the Iron Gates. It clearly shows that the riverwas diverted, because of such frequent dangers,so making navigation safer.

The best description of the remains andlocation of the Roman channel was provided byFelix Kanitz, a 19th-century Hungarian researcher

and travel writer. He noted large and regularearth banks, 14 m high, and with the distancebetween them 10 m at the base and 75 m at thetops of the banks, and concluded that they werepart of an ancient channel, partially preserved fora length of approximately 3220 m (Petrovic, 1970:33–4). During the field survey of 1969, the remainswere considerably less visible, but neverthelessthey showed a strong resemblance with Kanitz’snotes. Today they have completely disappearedunder the artificial lake.

Figure 2. General plan of the excavated site (1979–1982). 1. The remains of Trajan’s bridge; 2. The Castellum Pontes. (AfterGarasanin and Vasiç, 1980)




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Considerable Roman building activity in theIron Gates in the 1st century, especially the workof Trajan in the Lower Gorge, conducted duringa relatively short period of less than 10 years,reflects the undeniable importance the prepara-tions for the Dacian wars had for the Empire. It

also underlines the strategic importance offeredby this terrain.

Overview of the historical sources

Trajan’s Commentaries on the Dacian Wars

, andthe text of Apollodorus, the most importantwritten sources regarding the construction of thebridge, do not survive (the only part of Trajan’swork is a sentence referring to the First DacianWar found in Priscian (Gara

s

anin and Vasi

ç

, 1980:26). Apart from Trajan’s Column in Rome, andcoins minted by AD 106 commemorating thebuilding of the bridge, the only sources areCassius Dio, Procopius of Caesarea, and theByzantine poet Tzetses.

By analysing these surviving historical sources,we encounter numerous uncertainties regardingthe construction and superstructure of thebridge. The information provided by thesewriters, or gathered during previous researchconducted on the right riverbank, were neverstudied systematically until 1979 (apart from D.Tudor in his study of Roman bridges on theLower Danube (1974: 30–135). The order of events

given by Cassius Dio undoubtedly indicates thatthe bridge was built after the First Dacian Warand before the second Dacian campaign, between103 and 105. According to him the stone bridgewas erected at the point where the river wasgetting narrower, faster and deeper. Dio alsogives us information about the dimensions of 20piers in the river-bed (18–19 m wide; 50 m high;spacing 56.7 m) (Tudor, 1974: 67–8). He claimsthe bridge went out of use during the reign of Hadrian (117–138) (Dio: LXVIII).

In his description (Book 4), Procopius uses as a

source the lost text of Apollodorus of Damascus.According to him the building of the bridge andthe two castella

was contemporaneous (earlyexcavations at Drobeta showed that the castellum

existed between the reigns of Trajan and Justinian,with several changes in its plan of construction).He also mentions a diversion of the course of theriver during the building phases, and the laterdestruction of the bridge (Tudor, 1974: 68).Tzetses claims that Apollodorus used cofferdamsfor building the piers (Tudor, 1974: 69). Scenes 98

and 99 on Trajan’s Column (Fig. 3, top) andrepresentations on coins (Fig. 4) show that thesuperstructure of the bridge was made of wood.Stronger material is visible between the cutwaterpier and the arches, which were made of stone.Figures depicted on portals can be identified as

statues or trophies.

3

Scene 101 is equallyimportant (Fig. 3, bottom left). We can see theexit of the bridge in front of the portal withsoldiers who continue to march on solid ground,and (Fig. 3, bottom right) what might show a bitof the second bridge. The existence of anotherbridge could explain the plural form in the nameof Pontes (Popovi

ç

, 2003: 261).Historical facts concerning the forts are

scarcer. Procopius (Tudor, 1974: 67–8) states thatthe two castella

(Drobeta and Pontes) were builtat the same time as the bridge and that Justinianhad only reconstructed the one on the right bank(Pontes). This fort was mentioned in the NotitiaDignitatum by the name of Transdrobeta, theseat of the prefect of a detachment of the LegioXIII Gemina (Gara

s

anin and Vasi

ç

, 1980: 27).The Roman portrait in the National Museum inBelgrade (so-called ‘Trajan’s father’) could berelated to the sculptures from the portal. It wasdiscovered by the Danube in 1850, not far fromTrajan’s bridge.

Contradictions, and further analyses of

the sources

The following presents simply a definition of certain problems, which can be solved only byfurther research. There is a contradiction betweenthe information given by Dio Cassius and imagesof the bridge. According to Dio it was builtentirely in stone, while the images, especiallythose on Trajan’s Column, indicate a woodensuperstructure. Dio gives us an inexact descriptionof the Danube’s course, and the conclusionsdrawn from the texts of Procopius are probablycloser to reality (Procopius: IV, 6). The river was

not deep at that spot before the dam was created.The stream-bed was stable, covered with gravel,which made the construction of the piers easier.Dio’s statement that the river was fast and deepat that spot requires a more detailed analysis of the passage where he mentions bifurcation(Tudor, 1974: 68).

Before the level of the water was raised, asandbar had been located on the north side of theriver, attached to Simian island (Fig. 5), wherethe river was deeper. At first glance it is possible





to accept that the sandbar could have caused thechange in the course of the river, directing theflow towards the north (left) side. Nevertheless itis more probable to consider the possibility of existence of a branch which separated from themain flow of the Danube near Kladovo, only to

join it later near the village of Mala Vrbica. Thisbranch is still visible today in a shape of a large

and marshy valley. Changing the flow of the riverdid not represent a great obstacle for Romanarchitects. It is enough to remember their workon the channel near Sip. Gara

s

anin and Tudorwere convinced that this change was made byApollodorus when he built the bridge (Gara

s

aninand Vasi

ç

, 1980: 26), as it allowed him to buildthe great majority of the piers out of water.

Figure 3. Scenes 99–101 of Trajan’s Column, showing (top), the bridge with a portal, (bottom left) troops coming off a rampat the end of the bridge, (bottom right) an arched shape which may represent a second bridge.




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Caissons were necessary only in the places wherethe river was deeper (closer to the north bank). Itgoes without saying that without further researchon the piers in the Danube, this subject can notbe considered seriously.

Gara

s

anin examined the possibility of theexistence of another bridge, which could havebeen built either over the branch of the Danubeor over the above-mentioned valley. The secondassumption proposes that the bridge was con-necting the access-ramp of the Danube bridge

with the western door of the fort, which is largeenough to allow us to consider the existence of abridge. A counter-argument to the first possibilityis that the part of the image on scene 101 onTrajan’s Column, which represents firm soilbetween the two bridges, is too small. On the

other hand, the second hypothesis seems to bechallenged by the image of the two bridges asparallel, when the second one should be connectedto the fort on the way to the main bridge. In thesame scene we can see a flow of water crossed bythe bridge, which does not fit with the valleytoday. It seems that none of these arguments isconvincing enough. Although none of the imagescan be interpreted literally, presentation of waterbeneath the second bridge is somewhat dubious.On the other hand the fact that one episode of history was framed within the restrainingdimensions of a column scene means that theproportions of the surrounding countryside maywell not be realistic.

Analogies, former research andreconstruction

The portals of the Danube bridge can bevisualized with the help of another Trajanicbridge of the same period, at Alcàntara (Fig. 6).Colossal remains of the Danube bridge and itsmonumental architecture have always attractedthe attention of travellers, cartographers and

explorers. Their observations can be useful forunderstanding the bridge and the forts, eventhough they were not accompanied by systematicresearch on the spot. Marsigli stands out, as the

author of Danubius Pannonico Mysicus

(1726), wherehe discusses the Antique period and gives his ownview of the bridge and the forts accompanied by ageneral map (Gara

s

anin and Vasi

ç

, 1980: 26).The fort on the right bank is described andpresented on a map as a rectangular constructionwith sides of 89 and 112 m (notably close to theestimates made before the excavations of 1979).

After him, it was Kanitz who expressed interestin the bridge and the forts, specially the one onthe right side (1985: 34–45). He refers to olderbibliographic data and partly to reports writtenwhen the water was very low. In 1858, during anexceptionally low water-level of the Danube, theremains of the bridge appeared on the surface(this happened again in 1932). It is important topoint out that 16 piers were observed (contraryto the information given by ancient authors,who mention 20 piers). In 1909 two piers were

Figure 4. Reverse of the coin minted by the Senate in 106AD. (Reproduced by kind permission of Mr Steve L. Rub-

inger, Antiqua Inc.)

Figure 5. Topographical map of the Kladovo region. (AfterGarasanin and Vasiç, 1980)





destroyed close to the Romanian bank, becausethey were impeding navigation. The engineer incharge, Mr Popescu, did not leave any writteninformation on this subject. However, owing to

certain explanations left by him to D. Tudor, andcertain parts of the piers partially preserved inthe Turnu Severin museum (two wooden beamsof different dimensions and quadrangularsection, and stone blocks of different dimensionswith grooves on their interior sides), it is possibleto make general conclusions concerning thetechnique of construction (Tudor, 1974: 24). Oneof the important features of the two destroyedpiers was the construction of wooden beams whichsurrounded them. This confirms the existence of cofferdams, mentioned by Tzetses (Tudor, 1974:

85–6). Indirect survey of Trajan’s bridge wasorganized twice in the past, in 1932 and 1982.One photograph was published as the result of the first survey (Tudor, 1974: 130). It allowedTudor to distinguish only an outline of a form inthe river, not sufficient enough for determiningthe exact position of the piers.

4

The engineer E. Duperrex published in 1907 theresults of his research of the bridge along with thefacts known at that time. He offered a remarkablydetailed reconstruction (Fig. 7) (Gara

s

anin and

Vasi

ç

, 1980: 28). The model is in the Museum of Turnu Severin (Fig. 8). We can see two portals aswell as the whole construction of the bridge withcutwater piers and the ones on the land. There

are twenty of them. Trophy statues whichdecorated the portals are also shown. On thesouth bank, Dupperex inserted two piers betweenthe cutwater pier and the portal, while he madeonly one on the north bank. All the piers andportals are covered on the surface with stone.The piers standing in the river-bed support awooden superstructure. His estimation of thebridge’s length is 1133.9 m, 1071 m actually inthe river-bed (Tudor, 1974: 85–6). The onlyvisible flaw of the reconstruction is the additionof a downstream beak on the first cutwater pier

of the right bank, which does not exist.

Systematic excavation of the bridge

The excavations defined the elements of access tothe bridge, that is the remains of the portal andpiers on land (the dimensions, distance and con-struction method). The questions defined earlier,regarding the existence of a second bridge, andfinal dimensions of the Danube bridge, are yet tobe answered by new campaigns of archaeological

Figure 6. Alcàntara bridge. (Reproduced by kind permission of Ms Mediç)




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excavation. It was not possible to establish theexact depth of the cutwater pier foundations,which would allow us approximately to determinethe depth of those in the stream-bed, because of the water-table. The following presents the mostimportant technical information of the excava-tion. A 170 ×

120 m grid (divided into 10 ×

10 munits), oriented N-S, was made to cover the areaof the larger Castellum, Trajan’s bridge and thevalley (Fig. 2). Terrace excavation was necessarygiven the steep slope (Fig. 9).

Interpretation of the data

The orientation of the bridge deviated from thegeneral N-S direction by 8

°

to the west. Only thefoundations of the piers were preserved, exceptfor the cutwater pier (Fig. 10). When the pierbases were constructed, pits were dug into thelayer of compact gravel and their dimensionswere identical to those of the piers (Gara

s

aninand Vasi

ç

, 1980: 32). The pits were filled withstone and mortar (

opus caementicium

). This masswas carefully pressed until it became compact.

Horizontal and vertical cavities on the platformof the cutwater pier served for the location of wooden beams. Horizontal ones supported theroadway, and vertical ones consolidated the con-struction and facilitated the circulation of air toaccelerate the drying of the mortar. This clearlyproves that the roadway over the Danube wasmade of wood. Two pilasters mount the base of the cutwater pier (Fig. 11) and support the super-structure of the bridge. It seems that the absenceof a downstream beak proves that the pier was

Figure 7. Nineteenth-century reconstruction of the bridge by E. Dupperex.

Figure 8. Model of the bridge.

Figure 9. Old photograph showing general view of the piers of Trajan’s bridge.





not in the water when it was built. The pier wasconstructed in two parallel brick lines, whichformed a frame for a mass of stone and mortar.The bricks used belong to several types. The most

important ones are triangular or polygonal, andwere specially made for the upstream beak. Thereis a possibility that this kind of brick model wasdesigned by bridge constructors if not Apollodorushimself.

The construction of the other three piers issimilar to that of the cutwater pier. Additionalsupport bases were noted in the zone of theirfoundations to the east and west for static rein-forcement. Piers II and III have stone coating.The fourth pier is the most monumental. Special

attention was given to its lateral annexes, whichare considerably larger than those of other piers.There is no doubt that it represented the base forthe portal of the bridge. This fourth pier does not

have any coating, which indicates the possibleexistence of an access ramp, which has sincedisappeared. A survey conducted along the axisof the bridge, 10 m from that spot, did not giveany answer, since the layers were disturbed by anintrusion from the Middle Ages (Gara

s

anin andVasi

ç, 1980: 34). Further information led to theconclusion that the piers were made using thesame technique, and that the first three piers haveapproximately the same dimensions. This firstarchaeological campaign confirmed the primary

Figure 10. Side section of the remains of the bridge. (After Garasanin and Vasiç, 1980)

Figure 11. Horizontal plan of the first cutwater pier. (After Garasanin and Vasiç, 1980)



NAUTICAL ARCHAEOLOGY, 38.2


assumption that the access part of the bridge hadmasonry arches. All the dimensions of Trajan’sbridge have not yet been clearly determined; weare yet to establish the exact dimensions of all thecutwater piers.

Underwater surveyResearch started in September 2003, as a part of the project of the Institute for the Protection of Cultural Monuments of Serbia. The only viableresults were obtained by multibeam sonar sweepingof the whole route of the bridge, after obtainingall the necessary permits for conducting activitiesin international and Romanian waters. For thesurvey in the zone of the remains of the bridge,the public institution Plovput was engaged sinceit owned the most sophisticated equipment inSerbia for such activities. The measuring wasdone by Fansweep 20, which is specially designedfor work in shallow waters. The opening angle of the system is wide, generally varying between 90°

and 150°, and offers a wider coverage than earliersystems. Its two antennas in the shape of theletter V were placed in a boat specially constructedfor hydrographical measurement.

The measurements were taken on 16 September2003. The central line of the bridge (Fig. 12) wasbased on the remains of the piers on both sides,and 100 m were covered upstream and downstreamfrom this line. The boat was moving in 30

projected profiles in the sense parallel with thecurrent, with sweeping coverage six times biggerthan the vertical depth. That way, the stream-bedwas completely covered.

The general plan of the surveyed zone ispresented on a scale of 1:5000. The distancebetween the isolignes (isohypses) is 0.5 m. Thelegend gives the values, which extend from 38 to22 m. It is an image of different altimetric valuesrepresented by various colours, which are relatedto the height of the water-surface at the momentof the survey (40.36 m). The depths presented on

the plan vary between 2.3 and 18.3 m. Startingfrom the right bank we can distinguish 9 piers(shown as yellow assemblages in green surround-ings), while on the Romanian side an 18-m-deepdepression is visible (blue area in greensurroundings).

During the 2003 survey it was obvious, evenbefore a more precise scientific study of thecollected documents, that several changes hadoccurred since the creation of the Djerdap II damin 1984. A large quantity of sandy sediment was

noticed on the surviving piers. Moreover, it waspossible to locate with precision the remains of onlynine piers, starting from the right bank (Fig. 13).Piers 11, 12, 13 and 14 are no longer visibleunder the sand. Close to the left bank, because of intensive dredging in the zone of the bridge, theremains are not visible any more. Apart fromthe disappearance of 4 piers on the Romanianside and the complete destruction in 1909 of two

adjacent piers, which were obstructing navigation,the extraction of sand and gravel has caused thedeepening of this part of the bed by up to 18 m.

The length of the central line between the pierswith portals is 1097 m. The distance between thefirst and second cutwater piers in the stream-bedis 81 m. The axial distance between the subsequentpiers is 55 m. A visual underwater survey wasalso carried out over a length of 320 m startingfrom the right bank. Due to considerable sandsedimentation and bad visibility, the remains of

Figure 12. General plan of the surveyed zone. (Reproduced

by kind permission of Mrs Karoviç)





the first two piers, which were visible before therise of water, could not be seen any more. Onlythe outlines of the third and fourth piers werevisible under the sand. Given that the fifth andthe sixth are located in the zone of the principalcurrent, the sedimentation is minimal. Thepreserved remains of these two piers appear likea structure of crushed stone and mortar, locatedat a depth between 8 and 8.5 m with a height of 80 cm.

Thanks to this 3-dimensional image, one candistinguish with certainty the form of the remainsof 9 piers (from cutwater pier 2 to pier 10). Thethick sand layer covers piers 11 and 12, but thelayouts created by the current allow us to locate

them. For piers 13 and 14 we cannot give preciseinformation at this moment. The image of therelief of the river-bed, also obtained, enabled theobservation of the profile of these layouts (Fig. 14).Finally we must point out that an agreement withthe establishment Plovput was made on the physicalprotection of this site. In the zone around theremains of the Trajan’s bridge, in Serbian waters,the execution of any kind of work which couldendanger them is prohibited.

Conclusion

I would like to underline above all that thissurvey in Serbia proved for the first time thatmultibeam sonar, originally used for the needs of controlling the river navigability, could also beemployed in demanding archaeological inves-tigations. I would also like to explain why we needto continue research on this gigantic monument.First of all, the exact number of the remainingpiers has still to be determined. Nowadays, of the 20 original piers embedded in the stream-bed,

we are sure of the location of only 10. Documentsinform us about the disappearance of 6, therefore14 piers should remain. The inability of geophy-sical survey to locate four of these proves that adirect survey is necessary.

The date of the abandonment and destructionof the bridge still needs to be established. A

passage of Dio states that the intervention of Hadrian in this direction could not be understoodas the final abandonment. This is contradicted byHadrian’s policy in Dacia, which included thefounding of many municipia in that province.Bearing this in mind it seems extremelyimprobable that Hadrian destroyed for ever thisstable and solid communication with the pro-vince of Dacia. If we accept this, there is no datato confirm that the bridge was rebuilt later.However Historia Augusta informs us that: ‘The

Figure 13. Three-dimensional image of the route of the bridge (red lines represent the traces of the stream erosion).(Reproduced by kind permission of Mrs Karoviç)

Figure 14. The configuration of the river-bed (the red line

represent the profile of the traces of the stream erosion).(Reproduced by kind permission of Mrs Karoviç)



NAUTICAL ARCHAEOLOGY, 38.2


bridges which Trajan had built he restoredalmost everywhere, and he constructed new ones,too, but on those that he restored he retainedTrajan’s name’ (1924: 230). All these questionscan be solved only with new excavations of theCastellum Pontes and the bridge.

We must completely understand the construc-tion method of the bridge, and clarify in parti-cular the problems of the river diversion, whichprofessor Garasanin thought to have beenundertaken by Apollodorus. This enabled thebuilding of the greatest part of the piers withoutcofferdams, which were necessary only where theriver was deep. The questions cannot be seriouslyexamined without exact data about the piers inthe river-bed. The depth of the pier foundationsin the stream-bed is also yet to be defined. Thefact that the fourth pier has no coating is the lastproblem. One can thus expect the existence of an

additional pier or an access ramp, which hassince disappeared.

Finally it is necessary to point out that thedocuments obtained by the underwater survey of this remarkable cultural monument are thefundamental starting point for the next phase of

research. The first steps of future research will bedevoted to the meticulous study of the architectureof the bridge, which has never been undertaken,and which would lead, as professor Garasaninhoped, to an ideal reconstruction of the bridge.Given the fact that the remains of the bridge arehighly endangered by the river traffic and naturalinfluences, further research would raise the levelof awareness of their importance and result inbetter protection and conservation, as one of themost important monuments of the culturalheritage not only of Serbia and Romania but of Europe as well.

Acknowledgements

The author would like to thank Mme Karovic for her cooperation, Professor Rieth, Mme Marija Serban for translating, theanonymous reviewer for helpful criticism, and Mme Paula Martin for editing the paper.

Notes

1. In the compliments paid to the emperors on their accession, it became customary to wish that they might be more fortunatethan Augustus and more virtuous than Trajan (AD 98–117).

2. By the mid-3rd century AD, the province of Dacia was untenable for Rome and was left to the Goths by Aurelian in 270AD. Later still, Constantine brought it back symbolically under Roman rule through allied Visigoths, but it was never againgarrisoned by Roman legions. On the other hand, Trajan’s conquests in Mesopotamia were surrendered by Hadrian, who

considered them to be indefensible.3. Denominative analogies of the forts situated on both sides of Danube are known in Upper Moesia (ex. Dierna – Transdierna). The name Transdrobeta is attested in Notitia Dignitatum. The appearance of these two names in historicsources might be connected to the existence of two castella on the right bank of the river.

4. The copy of the photograph is too dark to be included in this article.

References

Garasanin, M. and Vasiç, M., 1980, Trajanov Most i kastel Pontes (Trajan’s Bridge and Castellum Pontes), preliminarni raportza 1979, Djerdapske sveske 1, 25–41.

Giurescu, C., 1981, Istoria ilustrata a românilor. Bucharest.Historia Augusta, 1924, Loeb Classical Library. Harvard.Jordovic, C., 1983, Ostaci rimskog puta u Djerdapskoj klisuri (Remains of the Roman road in the Iron Gates), Starinar 25,

365–72.Kanic, F., 1985, Srbija, Zemlja i Stanovnistvo (Serbia, Country and Population). Belgrade.Karoviç, G., 2005, Podvodna arheoloska istrazivanja ostatka Trajanovog mosta (Underwater archaeological research on the

remains of Trajan’s Bridge), preliminarni raport za 2004, Glasnik DSK 28, 64–7.Petrovic, P., 1970, Nova Trajanova Tabla u Djerdapu (The new Trajanic Inscription in the Iron Gates), Starinar 20, 31–40.Popoviç, A., 2003, Procopius’ pontes: One or two Trajan’s bridges?, Starinar 53–4, 255–61.Tudor, D., 1974, Les ponts romains du Bas Danube. Bucharest.

Serban, Trajan’s Bridge Over the Danube

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