Aosta Valley is the northwesternmost and smallest Italian region, with an area of about 3200 km² and 125,000 inhabitants. It can be considered the most mountainous region in the whole Europe, being directly surrounded by an uninterrupted mountain range including Alps massifs higher than 4000 m a.s.l.; about 5% of its surface is occupied by glaciers and the average altitude is 2100 m a.s.l..
The main bottom valley is about 90 km long, its altitude decreasing from the west (1200 m a.s.l. in Courmayeur, at the foot of Mt. Blanc) to the east (350 m a.s.l. at the border with the Po plain); the municipality of the main town Aosta (580 m a.s.l.) is located in the middle of the valley axis and is the seat of an important steel plant. The valley is crossed by a highway representing, together with the Mont Blanc tunnel, a crucial transport corridor between Italy and France. Several mountain villages located in lateral valleys at 1500-2000 m a.s.l. are very well known as winter sport centres and for naturalistic attractions.
- Rocks are almost exclusively metamorphic.
- Average temperature and rainfall vary greatly depending on altitude and local slopes orientation.