Overview: The Yucatan is a paradox: a rainforest where rainfall is rare, with no major rivers or streams. Instead, beneath the forest floor lies a mysterious ecosystem, an elaborate web of flooded caves known as 'cenotes'--Mayan for 'sacred wells'. More people have walked on the moon than have reached the end of these caverns, but their presence has fueled an astonishing diversity of life: from trees with hundred foot roots that still draw water, to a rich tapestry of exotic animals--like the howler monkeys whose cries fill the lush undergrowth.