Canyon de Furnas

What you are looking down into is a reservoir, so the water sits deep green between pale sheer walls and the whole thing is much bigger than any one photograph of it. I did it from the viewpoints along the top rather than from a boat, and that turned out to be the right way round - you get the shape of the canyon from up there, and you can walk between four or five of them in a morning. Go before midday. By the time the sun is overhead the water goes flat and loses the colour completely. There is a waterfall on the way in that drops into a pool so green it looks lit from underneath, and the lake on the drive back at sunset was worth stopping the car for.