North of the city center is the Arc de Triomphe, which once straddled the Via Agrippa between Lyon and Arles. Three arches support a heavy double attic (horizontal top) floridly decorated with battle scenes and marine symbols, references to Augustus's victories at Actium. The arch, which dates from about 20 BC, is superbly preserved, particularly the north side, but to view it on foot, you'll have to cross a roundabout seething with traffic.
Av. de l'Arc de Triomphe, Orange, 84100, France