Explore sinkholes and underground caverns at the 268-acre Rio Camuy (kahm-WEE) Cave Park, about 75 minutes west of San Juan. Since tours are limited, it’s best to arrive before 9:00 a.m. so that you won’t have to wait long or be disappointed by frequent afternoon rains that may cause the caves to close. A tram ride takes you into the 170-foot-high Cueva Clara (Clara Cave) and to a platform from which you can view the 400-foot-deep Tres Pueblos sinkhole.

For more of a challenge, sign on with Aventuras Tierro Adentro, an adventure tour company, to explore the park’s Angels Cave. You can forget about the tram. For this tour, you and your teens (ages 15 and older) hurtle across a zip line (a cable) and then rappel 250 feet into the mouth of the sinkhole.