Emosson Dam

The Emosson dam, 180 metres high and built in 1969-1973 over an older dam of 1925, holds back a reservoir of about 3.3 square kilometres at 1,930 metres in a bowl facing the Mont Blanc massif, and the approach is an oddity in itself - a combination of funicular, a tiny panoramic train and an inclined lift, built for the construction work and now carrying visitors. The scientific interest is above the lake: in 1976 a hiker noticed marks on a sloping slab of Triassic sandstone that turned out to be dinosaur footprints, hundreds of them in trackways left about two hundred and forty million years ago when this rock was a shoreline, long before the Alps existed. Reaching the site is a walk of a couple of hours from the dam over rough ground.

What to look for

• Triassic dinosaur trackways - hundreds of prints found by a hiker in 1976.
• A high arch dam - the reservoir at nearly 2,000 metres facing Mont Blanc.
• A works transport chain - funicular, small train and inclined lift.
• Rock older than the Alps - a shoreline slab now tilted at altitude.

When to go

Late June to September. A day.

Practical notes

The trackway site is a two-hour walk each way on rough ground and the prints are faint - low sun helps. The transport chain runs seasonally and to limited timetables. Weather at the dam turns quickly. Facilities are minimal.

Nearby

Finhaut and the Trient valley are below; Chamonix is over the border.