Enter the exciting world of rivers that disappear into the underworld as you float on inner tubes with only headlights to light your way after a 1 ½ hr drive from San Ignacio. Spectacular crystal formations of million years in the making. Massive cathedral-sized chambers with walls of river-sculptured rock. Imagine the experience as you float through a subterranean cathedral. Turn off your lights, leaving you with the sensation of drifting in a black void of timelessness and into the sacred realm of the ancient Maya.