Park at the Col de la Colombiere. There is quite a lot of parking spread along the road but I advise that you get there early to secure your place as this is a busy place, people come to eat at the restaurant, walk or just to visit.
(S) From the parking, take the broad path on the left of the restaurant.
(1) At the first obvious bend, turn right and continue along the broad track this ascends to the Chalet de la Colombiere (farm building)
(2) From the farm, take the path heading uphill. This goes through many zig-zags and in parts splits and rejoins again. It is very eroded in places, especially near the top just before the slope eases back.
(3) At the lake, there are lots of goats and usually a human-friendly herd/guard dog. To get back, retrace your steps back downhill to the parking. (E)