The city has three triumphal arches and several portals that have been preserved in place of the destroyed fortress walls. Of greatest interest is Trajan's Arch (Arca di Traiano), erected in 115 in honor of the emperor, who turned the city harbor into a fortified port. Walking under it is a little scary. On the other hand, what has stood for 2000 years is unlikely to fall on your head specifically. Well, if it collapses, then it deserves it.