There is so much to see and do in Puerto Rico that the unaware visitor might be overwhelmed and end up missing some of the best sights the island has to offer. To help you prioritize, here are my votes for the top 5 attractions on the island. Included are an ancient fortress; a tropical rainforest; a bioluminescent bay; a natural underground cave system; and a tiny islet with breathtaking beaches.
The Castillo de San Felipe del Morro, (more commonly known as El Morro) is Old San Juan's most recognizable landmark. For over 400 years, it has protected San Juan and the shipping route from the New World to the Old. Today, a visit to this six-level citadel is like walking through a military history of Puerto Rico from the 1500s to the 20th Century. Pass by cannons still facing the ocean, step inside a sentry box, see how the soldiers used to live and work in colonial times, and check out the enhancements made by the U.S. during World War II.
Try to go on a moonless night. When there is a little light and you're kayaking through mangrove trees out into Mosquito Bay on Vieques Island, you might wonder what all the fuss is about. And then you'll notice that your oars are glowing green in the water. Fish streak away from you like underwater lightning. And then you'll understand why the Vieques Biobay is one of the most amazing experiences Puerto Rico has to offer. Thanks to its geography, climate, and local conservation efforts, the Vieques Biobay is one of the most bioluminescent bays in the world.
El Yunque, or "The Anvil," is home to the only tropical rainforest in the U.S. National Forest System. A two-hour drive from San Juan, this lush, mountainous terrain is about as far removed from the city's beaches and resorts as you can get. But that's why people come here: to walk among the rainforest's abundant flora; to hike along one of several trails ranging from easy walks to difficult climbs, and to dive under a waterfall. This is a part of Puerto Rico that hasn't changed in centuries.
On tiny Culebra Island, off Puerto Rico's eastern coast, the star attraction is generally considered to be the admittedly spectacular Flamenco Beach. But we prefer Culebrita for its isolation (you have to take a water taxi or private boat to get here), its unspoiled beauty (the lighthouse here is the only one manmade structure on the island), and yes, even its beaches. West Beach is a long stretch of sand hugging the coastline with waters several shades of blue and terrific snorkeling. The Culebrita Reef is on the south side of the island. And the island's crown jewel is Playa Tortuga (“Turtle Beach”), a picture-perfect crescent of sand loved by both nesting turtles and humans.
We're going to cheat a little bit here. The Río Camuy Cave Park edges out close competitors like the Museum of Art in Ponce for two reasons: One, you can combine it with a visit to the awesome Arecibo radio telescope (most tour companies offer a package trip). And two, you can enjoy some seriously adventurous trips out here. The Camuy cave system is the third largest in the world. The tour through the caves takes you through subterranean ravines to the edge of caves over 600 feet deep, as well as an underground river. The more active and daring can take an eco-excursion out here, which involves rappeling down the mouth of one of the caves, mud-sliding, body rafting, and free jumping through this subterranean world.