Aosta (UK: //, US: //, Italian: [aˈɔsta] (listen); French: Aoste [ɔst],[a] formerly Aouste; Francoprovençal: Aoûta [aˈuta], Veulla [ˈvəla] or Ouhta [ˈuhta]; Latin: Augusta Praetoria Salassorum; Walser: Augschtal; Piedmontese: Osta) is the principal city of Aosta Valley, a bilingual region in the Italian Alps, 110 km (68 mi) 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 Pass routes.
Aosta was settled in proto-historic times and later became a centre of the Salassi, many of whom were killed or sold into slavery by the Romans in 25 BC. The campaign was led by Terentius Varro, who then founded the Roman colony of Augusta Praetoria Salassorum, housing 3,000 retired veterans. After 11 BC Aosta became the capital of the Alpes Graies ("Grey Alps") province of the Empire. Its position at the confluence of two rivers, at the end of the Great and the Little St Bernard Pass, gave it considerable military importance, and its layout was that of a Roman military camp.
After the fall of the Western Empire, the city was conquered, in turn, by the Burgundians, the Ostrogoths, and the Byzantines. The Lombards, who had annexed it to their Italian kingdom, were expelled by the Frankish Empire under Pepin the Short. Under his son, Charlemagne, Aosta acquired importance as a post on the Via Francigena, leading from Aachen to Italy. After 888 AD it was part of the renewed Kingdom of Italy under Arduin of Ivrea and Berengar of Friuli.
The privilege of holding the assembly of the states-general was granted to the inhabitants in 1189. An executive council was nominated from this body in 1536, and continued to exist until 1802. After the Congress of Vienna restored the rule of Savoy it was reconstituted and formally recognized by Charles Albert of Sardinia, at the birth of his grandson Prince Amedeo, who was created duke of Aosta.
Aosta has either a warm-summer humid continental climate (Köppen climate classification: Dfb), or a subtropical highland climate (Köppen climate classification: Cfb). It is considered temperate continental (Dc) in the Trewartha climate classification.