Lac de Joux

The Vallée de Joux is a long trough in the Vaud Jura, closed at both ends, with a lake filling much of its floor at about a thousand metres. It is the largest lake in the range. The water drains underground rather than by a river, disappearing into fissures at the northern end, and the valley around it is pine forest, stone farms and a string of villages that have made watch movements for two centuries. In summer the lake is used for sailing and windsurfing, helped by a reliable afternoon wind, and in cold winters it freezes hard enough to walk and skate on, which is when the valley fills with people from the lowlands.

What you actually see

• The lake itself - open water at a thousand metres with wooded ridges on both sides.
• The Dent de Vaulion - a ridge above the valley with a long view over the lake.
• The watchmaking villages - Le Sentier and Le Brassus, making movements for generations.
• Winter ice - skating and walking on the frozen surface in cold years.

When to go

June to September for sailing, for swimming in water that never gets truly warm, and for the ridge walks above the valley. Deep winter is the other season, for cross country skiing on the valley trails and, when the ice is thick and formally opened, for skating. Ice is not guaranteed in any given year.

Honest expectations

The valley is high, damp and noticeably colder than the lowlands; fog and flat grey weather are common and it can feel bleak on anything but a fine day. The shore is developed in places and the water is cold for swimming. Winter ice is only walkable once the authorities say so, and mild winters give none at all.

Nearby

Vallorbe and its caves at the end of the valley, with Lausanne about an hour away.