From the Introduction: Over the centuries wind and water have worn a narrow canyon, widening and narrowing on occasion, into the stone making up most of the local landscape. Nowadays the flow of the water follows other paths leaving this canyon, like most of the environs bone dry. Only some kind of large, almost spherical cactus has managed to prosper on the mostly bare rock, possibly providing sustenance if you manage to get past the spines. But maybe you should beware either whatever insects or other animals these cacti lure in with their large flowers or the cacti's lure of food and water itself.