The route is simple. From the hamlet of Casterino in the commune of Tende, take the narrow road after the Hôtel du Chamois to the end, where the car park at marker 394 marks the start of the hike.
(S/E) Follow the track, also used by 4x4s, to marker 374. After 35 minutes, you will pass marker 393, which leads to Lac de l'Agnel if you turn right.
(1) At marker 374 (1 hour 10 minutes), the track becomes a path. The path runs parallel to the stream, which descends gently through a small, very green valley. You will then arrive at some beautiful waterfalls (1 hour 35 minutes), one descending from Lac Vert (the one on the right) and the other from the left, which in my opinion is the most beautiful as you can see it on three levels.
(2) From there, the trail climbs more steeply, but it is well paved, allowing you to reach marker 98, which offers a choice between the Vallée des Merveilles or the Valmasque refuge.
(3) Turn right to reach the Valmasque refuge in ten minutes.
(4) Return via the same route to get back to the car park (S/E).

