San Juan Day Trips

Arecibo Ionospheric Observatory

America's ears and eyes are focused on the stars from the island of Puerto Rico. In the northwest mountains of the island about 90 minutes drive west of San Juan, among the Karst Country hills, is one of the most important astronomical research facilities on earth, the Arecibo Ionospheric Observatory. Its massive dish is larger in area than a dozen football fields and is sited in a sinkhole, aimed at the heavens and tuned to detect the slightest sounds emitted from the farthest stars. This is the home base for NASA's 'SETI' (Search for Extra-Terrestrial Intelligence) project and as such holds great fascination for visitors. A Visitors Centre is equipped with interactive exhibits to demonstrate how the huge structure works. Visitors can hike to the viewing platform to view the vast tiled dish.

Website: www.naic.edu; Telephone: 878 2612; Opening time: Open daily from 9am to 4pm in June, July, December and January. Closed on Mondays and Tuesdays in the remaining months ; Admission: US$5 (adults), US$3 (children)

Rio Camuy Cave Park

Well worth a day trip from San Juan is the incredible 268-acre Rio Camuy Cave Park, two hours south-west 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; Telephone: 898 3100; Opening time: Wednesday to Sunday 8am to 3.30pm; closed when raining; Admission: US$12 (adults), US$7 (children)