Arch of Drusus (c100). The Arch of Drusus is an ancient arch in Rome, Italy, close to the First Mile of the Appian Way and next to the Porta San Sebastiano. The exact origins of the Arch are unclear. It is now generally agreed that it has nothing to do with Nero Claudius Drusus, the conqueror of the Germans. Some versions have the arch being constructed as part of a spur added to the Aqua Marcia by Caracalla in 211-216 AD to take water from that aqueduct to Caracalla's new baths. However, it appears more likely that the arch predated the aqueduct and that the aqueduct was conveniently routed over the top of the arch. Only the central part of this arch is now standing, but it was originally triple, or at least with projections on each side, although never finished. It is built of travertine, faced with marble, and on each side of the archway are columns of Numidian marble with white marble bases. The archway is 7.21 metres high. The Aqua Antoniniana, the branch of the Aqua Marcia, ran over this arch, but the brick-faced concrete that is visible on the top seems to belong to a later period. The arch may possibly be the Arch of Trajan.