Grutas de Lanquín
Grutas de Lanquín information
Lonely Planet review
These caves are about 1km northwest of the town, and extend for several kilometers into the earth. There is now a ticket office here. The first cave has lights, but do take a powerful flashlight (torch) anyway. You'll also need shoes with good traction, as inside it's slippery with moisture and bat droppings.
Though the first few hundred meters of the cavern have been equipped with a walkway and are lit by diesel-powered electric lights, most of this subterranean system is untouched. If you are not an experienced spelunker, you shouldn't wander too far into the caves; the entire extent has yet to be explored, let alone mapped.
As well as featuring funky stalactites, mostly named for animals, these caves are crammed with bats. Try to time your visit to coincide with sunset, when hundreds of them fly out of the mouth of the cave in formations so dense they obscure the sky. For a dazzling display of navigation skills, sit at the entrance while they exit. Please be aware that bats are extremely light-sensitive and tempting as it may be, flash photography can disorient and, in some cases, blind them.
The river here gushes from the cave in clean, cool and delicious torrents. You can swim in the river, which has some comfortably hot pockets close to shore.