Aosta is the principal city of the bilingual Aosta Valley in the Italian Alps, 110km north-northwest of Turin. It is situated near the Italian entrance of the Mont Blanc Tunnel, at the confluence of the Buthier and the Dora Baltea, and at the junction of the Great and Little St. Bernard routes. Aosta is not the capital of the province, as these functions are shared by the region and the communes.

The main monuments of the city include:

• The Arch of Augustus, erected in 35 BC to celebrate the victory of the Roman troops led by consul Varro Murene over the local Salassi.
• The Porta Praetoria (1st century AD), once the eastern gate to the city, which has preserved its original forms apart from the marble covering. It is formed by two series of arches enclosing a small square.
• The Roman theatre, of which the southern façade remains today, 22 m tall. The structure, dating from the late reign of Augustus, occupied an area of 81 x 64 m: it could contain up to 4,000 spectators. In the nearby was the amphitheatre, built under Claudius.
• The Cathedral of Aosta, built in the 4th century and replaced in the 11th century by a new edifice dedicate to the Madonna. It is annexed to the Roman Forum.
• The Romanesque-Gothic Sant'Orso (Saint-Ours). Its most evocative feature is the ancient cloister, which can be entered through a hall on the left of the façade. It is dedicated to Ursus of Aosta.
• The Saint-Bénin College, built about 1000 by the Benedictines. It is now an exhibition site.
  Of the 20 towers of the Roman walls the following are well preserved:
• Tour du lépreux, which has been given this name after a leper was jailed there in the late 17th century. Le lépreux de la cité d'Aoste, a novel by Xavier de Maistre, was named after this tower.
• Tour Neuve (13th century).
• Tour du Pailleron.
• Tower (Castle) of Bramafan, built in the 11th century over a Roman bastion. It was the residence of the Savoy viscounts. The Franco-Provençal term Bramafan is translated as "He who screams for hunger".
• Tour du Baillage.
• Tour Fromage ("Cheese tower").