The two Lacs Merlet — a small upper lake and a larger lower one — sit in a high cirque south of Courchevel, just outside the boundary of the Vanoise National Park. The walk in is one of the best half-day hikes in the area: about three hours each way from the trailhead at Pralong, climbing through alpine pastures with marmots and the occasional ibex.
The water is a deep, mineral blue against the rock. The setting is austere — no trees, just stone, snow patches into July, and silence. There is a small refuge (the Refuge des Lacs Merlet) about half an hour below the lakes that serves food in summer and rents bunks if you want to stretch the visit into an overnight.