The first thing you become acutely aware of in a big cave is the darkness. After a while it seems to have a palpable presence. Another thing is that these caves are wet and noisy. There is almost always water flowing alongside the routes, and the water courses can be immense. There are 150-foot waterfalls in Cheve. And Bill Stone has described the noise from one particular waterfall in Huautla as being like standing next to a jetliner, and not being able to get away from it. Finally, supercaves tend to be characterized by vast open spaces. There are chambers in Cheve that could hold fifty diesel locomotives. The immensity of the spaces is counterintuitive.