(Aosta). A 2 mile wide valley in the Val d'Aosta (Cisalpine Gaul, northwestern Italy), flanked by high mountains. Standing at the Italian end of the Great and Little St. Bernard Passes over the Pennine and Graian Alps respectively, at the confluence of the rivers Duria Major (Dora Baltea), a tributary of the Padus (Po) and another stream, the Buthier, the place belonged to the Gallic tribe of the Salassi, who controlled the mining industry of the valley (including gold and iron); it was here that Augustus' general Aulus Terentius Varro Murena encamped in 25 BC when engaged in subjugating this recalcitrant people. As a sequel, in order to maintain the control thus established and assure communications with Gaul, the emperor replaced the camp by a military colony consisting of 3,000 retired praetorian guardsmen to whose branch of the army the new settlement owed its name. It became and remained the capital of the region; inscriptions record that the Salassi, at least later, gained civic rights in the community.

The center of modern Aosta preserves the Roman plan almost without change. Today's higher ground level has buried some of the Roman monuments, but those still visible are mostly of Augustan date. They include the arched rear wall of a theater or Odeon (originally roofed because of the climate), eight arcades of the amphitheater (unusually located within the city itself) and town walls, which make Augusta Praetoria one of the best preserved of all Roman fortified cities: although damaged, they survive for almost their whole rectangualr length together with two gates (including the triple, two-curtained Porta Praetoria) and a famous single-spanned Arch of Augustus adorned, on each face, with Corinthian columns supporting a Doric entablature.