The Glacier du Tour... there are several spots to land on the glacier, but the best is right at the top at over 11000ft.
You need full power to land, and drag yourself up the slope a bit. Then you judge your moment to turn round and face downhill, slide down the slope and take off. The take off can be done almost without power, if you're in the mood! (All this assumes, of course, that you haven't a) fallen into a crevasse, b) landed long and dropped off the precipice at the top or c) landed too short and got stuck...)
Click here to see some pictures of it.
They don't really do justice to it, but will give you an idea.
Needless to say, I haven't tried it without an instructor next to me. It's not at all difficult if you get it all right..... but it's also not at all difficult to get it all horribly wrong!!