These caves are only a few miles by car down a steep track, but ecologically speaking, they are in a different world. In the course of a few hundred yards, you drop from pine savanna to tropical forest. Few other places in Belize illustrate its extraordinary geological diversity as clearly as this startling transition. A river runs right through the center of the main cave—actually it's more of a tunnel, open at both ends—and, over the centuries, has carved the rock into fantastic shapes. Swallows fill the place, and at night ocelots and margays pad silently across the cold floor in search of slumbering prey. Seen from the dark interior, the light-filled world outside seems more intense and beautiful than ever. About a mile away (2 km) are the Cuevas Gemelas (Twin Caves), best seen with a guide. Due to occasional bandit activity in the area, at times a Belize Defence Forces escort is required to visit the Rio Frio Caves—if driving on your own, ask at your hotel or at the Douglas de Silva forestry station, where private vehicles meet up with a Defence Force escort.