The remains of Trajan’s bridge and Pontes castrum are located near the village of Kostol, 5 km downstream from Kladovo. The bridge, built between 103 and 105, is the work of the Syrian architect Apollodorus of Damascus. The length of the bridge with portals was 1133.90 m, and the part over the riverbed was 1071 m. The remains on the coastal part consist of four masonry columns connected by arches. There were 20 columns in the riverbed, whose axial span of 56.5 m was bridged by a wooden lattice structure. Simultaneously with the bridge, in the function of its defense, auxiliary camps Pontes on the right and Drobeta on the left bank of the Danube were built.
Pontes, approximately square in shape, was located downstream from the bridge and until the 6th century retained the function of defending this part of the limes. In addition to the basic points of the castrum – the ramparts, towers and gates – archeological research determined the plan and layout of the buildings inside the ramparts and stated that at the beginning of the 4th century, with the changes in the Roman army, a new concept of the interior of Pontes was created. Medieval settlements and necropolises with layers of the IX-X, XI-XII and XIV centuries were formed in the ancient fortification as well as in the area outside it. Protective archaeological excavations and conservation works began in 1979 as part of the Đerdap II project. The remains of the first four columns of the bridge have been secured against submersion by means of an anchor.