The 268-acre Parque de las Cavernas del Río Camuy contains one of the world's largest cave networks. After watching an introductory film, a tram takes you down a trail shaded by bamboo and banana trees to Cueva Clara, where the stalactites and stalagmites turn the entrance into a toothy grin. Hour long guided tours in English and Spanish lead you on foot through the 180-foot-high cave, which is teeming with wildlife. You're likely to see the blue-eyed river crabs and
long-legged tarantulas. More elusive are the bats that make their home here. They don't come out until dark, but you can feel the heat they generate at the cave's entrance. The visit ends with a tram ride to the Tres Pueblos sinkhole, where you can see the third-longest underground river in the world passing from one cave to another. Tours are first-come, first-served; plan to arrive early on weekends, when locals join the crowds. There's a picnic area, cafeteria, and gift shop.