City/Region: Camuy. Well worth a day trip from San Juan is the incredible 268-acre Camuy Cave Park, two hours southwest of the city. The park is the site of miles of subterranean caverns that were carved out of the limestone by the Camuy River more than a million years ago. Only seven miles (11km) of the caves have yet been fully explored, but 16 entrances have been discovered to what is believed to be the world's largest cave network. Well-maintained walking trails lead visitors down 200 feet (61m) into a fern-filled ravine to explore the cathedral-like caverns. Guided tours are available through one cave and two sinkholes, where you will see stalactites, stalagmites and plenty of bats. The caverns also contain a unique species of blindfish. The park has picnic areas, walking trails, food outlets, an exhibition hall and a souvenir shop.

Address: Route 129

Hours: Wednesday to Sunday 8am to 3:30pm; closed when raining

.