Grutas de Acocomoca

In the hills northeast of Tetela de Ocampo, near the Nahua community of Carreragco, a stream disappears into the rock and runs through a cave system known as the Grutas de Acocomoca. The name is usually translated from Nahuatl as "water that sounds," and inside you hear the river long before you see much of anything. The caves are said to have been found in 1997 and run for roughly 200 meters.

This is a wet, physical outing rather than a lit show cave. The entrance is low, so you stoop along the first passage, and before long the water reaches your waist. Further in, the passages narrow and climb over small steps in the rock, and helmet lamps pick out stalactites, columns and mineral-streaked walls that glitter yellow. The underground river ends at the sound of a waterfall echoing through the chambers.

Go with a local guide, who will provide helmets and lights, and bring clothes and shoes you do not mind soaking plus a dry change for afterward. It is not a good choice for anyone uneasy in tight, dark spaces.