There’s a tunnel into the military range at Lac Hongrin, it’s really only open at weekends as the range is in use and the tunnel is one-way on a schedule. It’s tricky to ride there from Leysin, the way down through the forest are really red/white hiking trails. We’ve had a bit of rain so it’s muddy and the track is too hard to ride in a couple of places for me! But it’s worth the effort, finally hitting the low meadows you can climb back up the road and ride all the way along the lake into Les Mosses before cutting across the mountain to Leysin.
As a tip, you could reverse the route easily, Leysin to Les Mosses, around the lake, through the tunnel and then descend all the way to Aigle using the train to return to Leysin.
