What could be more refreshing than starting your hike under the spray of the Py waterfall standing at 80m high! Ÿou will follow the mountain stream of the same name throughout the whole ascent towards the “Refuge de Plaisance”. In the mountains the variations in stream flow are impressive! In spring, the meltwater hurtles down the slopes at full speed while in the autumn the water subsides. The colour of the water can also change: a violent thunderstorm can quickly turn this clear water into black mud. A hundred years ago, it was still possible to pass between the waterfall and the wall without getting wet! This is unthinkable today, which just gœs to show how strong the eroding Py stream is.