Arecibo & Camuy

68 miles to 77 miles (109km-124km) W of San Juan

Getting There--Arecibo Observatory lies a 1 1/4-hour drive west of San Juan, outside the town of Arecibo. By car, take Road 22 towards Arecibo, then Road 129 and follow the signposts along a roller-coaster journey on narrow two-lane roads. Still following the signposts, you take routes 626 and 623, crossing the lush Valley of Río Tanamá until you reach Route 625, which will lead you to the entrance to the observatory.

On the same day you visit the Arecibo Observatory, you can also visit the Río Camuy caves. The caves also lie south of the town of Arecibo. Follow Route 129 southwest from Arecibo to the entrance of the caves, which are at km 18.9 along the route, north of the town of Lares. Like the observatory, the caves lie approximately 1 1/2 hours west of San Juan.

Exploring the Area--Dubbed "an ear to heaven," Observatorio de Arecibo (tel. 787/878-2612; www.naic.edu) contains the world's largest and most sensitive radar/radio-telescope. The telescope features a 20-acre (8-hectare) dish, or radio mirror, set in an ancient sinkhole. It's 1,000 feet (300m) in diameter and 167 feet (50m) deep, and it allows scientists to monitor natural radio emissions from distant galaxies, pulsars, and quasars, and to examine the ionosphere, the planets, and the moon using powerful radar signals. Used by scientists as part of the Search for Extraterrestrial Intelligence (SETI), this is the same site featured in the movie Contact with Jodie Foster. This research effort speculates that advanced civilizations elsewhere in the universe might also communicate via radio waves. The 10-year, $100 million search for life in space was launched on October 12, 1992, the 500-year anniversary of the New World's discovery by Columbus.

Unusually lush vegetation flourishes under the giant dish, including ferns, wild orchids, and begonias. Assorted creatures like mongooses, lizards, and dragonflies have also taken refuge there. Suspended in outlandish fashion above the dish is a 600-ton platform that resembles a space station.

This is not a site where you'll be launched into a Star Wars journey through the universe. You are allowed to walk around the platform, taking in views of this gigantic dish. At the Angel Ramos Foundation Visitor Center, you are treated to interactive exhibitions on the various planetary systems and introduced to the mystery of meteors and educated about intriguing weather phenomena.

Tours are available at the observatory Wednesday through Friday from noon to 4pm, Saturday and Sunday from 9am to 4pm. The cost is $4 for adults, $2 for children and seniors. There's a souvenir shop on the grounds. Plan to spend about 1 1/2 hours at the observatory.

Parque de las Cavernas del Río Camuy (Río Camuy Caves) (tel. 787/898-3100) contains the third-largest underground river in the world. It runs through a network of caves, canyons, and sinkholes that have been cut through the island's limestone base over the course of millions of years. Known to the pre-Columbian Taíno peoples, the caves came to the attention of speleologists in the 1950s; they were led to the site by local boys already familiar with some of the entrances to the system. The caves were opened to the public in 1986. Visitors should allow about 1 1/2 hours for the total experience.

Visitors first see a short film about the caves and then descend into the caverns in open-air trolleys. The trip takes you through a 200-foot (60m) deep sinkhole and a chasm where tropical trees, ferns, and flowers flourish, along with birds and butterflies. The trolley then goes to the entrance of Clara Cave of Epalme, one of 16 caves in the Camuy caves network, where visitors begin a 45-minute walk, viewing the majestic series of rooms rich in stalagmites, stalactites, and huge natural "sculptures" formed over the centuries.

Tres Pueblos Sinkhole, located on the boundaries of the Camuy, Hatillo, and Lares municipalities, measures 65 feet (20m) in diameter, with a depth of 400 feet (120m) -- room enough to fit all of El Morro Fortress in San Juan. In Tres Pueblos, visitors can walk along two platforms -- one on the Lares side, facing the town of Camuy, and the other on the Hatillo side, overlooking Tres Pueblos Cave and the Río Camuy.

The caves are open Wednesday through Sunday from 8am to 3pm. Tickets cost $10 for adults, $7 for children 4 to 12, and $5 for seniors. Parking is $2. For more information, phone the park.

Where to Dine--The closest place for food is the Casa Grande Mountain Retreat in Utuado, a little mountain town south of Arecibo.