The reliefs circumventing the Trajan column in Rome depict the most important events connected with two expeditions conducted by Emperor Trajan against the Dacians. One of the reliefs shows the outline of a road bridge. The likeness of the bridge is extremely detailed and retains the proportions of the construction elements , testfying to the fact that it was executed by an artist upon the basis of a technical drawing and not a handmade sketch or observation from nature. Consequently, we can treat the bridge portait in the relief as a faithful rendition of the erected object.The actual dimensions of the object can be estimated only by those familiar with the size of an element which remains constant for every such object, for example, the height of the balustrade.The acceptance of a given height made it a feasible to calculate the basic size of the bridge itself.Scarce historical sources and ruins of bearings confirm the existence of a bridge across the Danube in the region of Drobeta Nonetheless, difficulties with determining the main dimensions of the bridge rendered it impossible to recreate its appearance. Universal reference was, therefore, made to the likeness of the bridge presented in the relief as the bridge acros the Danube. In the opinion of Dion Cassius (155-235), the Danube bridge had 20 pillars 60 feet wide and 170 feet apart (50.32 m). The total height of the object amounted to 150 feet (44.40 m). References made in numerous publications to this height as one corresponding to the bridge pillars in uniconfirmed. The construction of the bridge spans was comprised of wooden arches supported by stone pillars. The bridge head was a brick construction with arch spans ending in a portal. The author of the article maintains that the wooden arches of the bridge spans were based on 20 free-standing pillars made of veneered stone blocks and on two pillars adjoining the brick heads. Consequently, there were 22 pillars and 21 spans (Cassius took into consideration only free standing pillars, and this estimation was quoted by other scholars as the total of the bridge pillars). The outcome of the measurmenets of the pillar remnants was confirmed by data contained in historical sources. A comparison of the prime dimensions of the Danube bridge with those of the bridge depicted in the relief indicates that particular construction elements of both objects are mutually proportionate. The two bridges were built according to identical construction rules. The stone arch was replaced by a much lighter vault made of wooden beams, which was erected incomparably quicker and introduced a uniform design rule. With such a premise, every bridge was a precise replica of the model solution, and their only difference was the applied scale. The sole exceptions were constant elements of the construction, which remain independent of the span, such as the height of the balustrade and the size of stone blocks in the pillars. The number of the spans and the height of the pillars, adapted to local conditions, could differ. Considerable doubts are connected with the question whether the bridge shown in the Trajan column relief is the construction raised across the Danube near Drobeta. Arguments in favour accentuate the outline of the bridge in the relief and its counterpart recreated upon the basis of historical sources, the measurements of the pillar ruins, as well as the hypothesis that the construction of the bridges was moulded by Apollodorus. The outlines of the bridges differ essentialy.