ARECIBO. You might recognize some areas of the observatory from the movie "Contact," part of which was filmed here. The facility is associated with Cornell University's National Astronomy and Ionosphere Center and boasts the world's largest radar-radio telescope. A visitor center features interactive learning opportunities on subjects such as weather, meteors and the solar system, but be sure to walk around the platform and view the dish in a sea of surrounding greenery. The observatory is about 50 miles from San Juan, but astronomy buffs and many others will find the trip extremely worthwhile.

CATAÑO. Sanjuaneros have Fidel Castro to thank for the world's largest rum distillery calling Puerto Rico home. Bacardi built their first distillery in Cuba in 1862. When the Castro regime confiscated the factory in the 1960s the family moved operations to Cataño, across San Juan Bay from the heart of the city. A short drive brings you to the "Cathedral of Rum" where you can take a free 45-minute guided tour of the facility. You will learn what it takes to produce 100,000 gallons per day of the heady concoction. A gift shop sells souvenirs and rare drinks bottled under the Bacardi label. There is also a small museum about the history of the Bacardi family.

This fascinating slice of wildlife is an easy day trip from San Juan. More than 100 billion gallons of rain falls each year on the 28,000-acre forest, so expect to get soggy on your hike. More than 240 species of trees are represented here, 50 species of ferns and 20 varieties of wild orchids. Keep your ears tuned for the chirping of the tiny coqui frog; El Yunque is one of his few remaining homes. To take best advantage of your time in the forest, consider taking a guided tour. The rangers know the best viewing and swimming spots.

Locals refer to this nature reserve as "El Faro" after the 19th-century lighthouse of the same name that is located here. Well-maintained trails and boardwalks crisscross the park, and observation decks provide dramatic views of El Yunque Rain Forest and the islands off Puerto Rico's coast. English language tours are available at 2pm. Advance reservations are required to visit the park.

CAMUY. Puerto Rico is home to some of the most important cave systems in the world. The Rio Camuy caves have been open to the public since 1986. An open-air trolley takes visitors deep into the earth where they can walk among stalactites and stalagmites. The newly opened Cathedral Cave costs an additional fee to visit and reservations must be made in advance, but the spectacular views of Taino Indian petroglyphs are worth the price. Visitors should wear non-slip walking shoes. A snackbar and gift shop are on the premises.