The Marble Caves, Chile This geological formation is of unusual beauty. These caves have formed in a pure marble and are bathed in the deep blue water of General Carrera Lake. The ice glaciers of Patagonian Andes contain small particles and, when the ice melts, many particles remain suspended in the water. This gives an unusual effect - the glacial meltwater is slightly turbid and it refracts the blue part of sunlight. Due to this the water of General Carrera Lake has a distinct blue color.