Puerto Rico packs a lot into a relatively small island — colonial history, tropical rainforest, offshore islands, and some of the Caribbean's best beaches. Most visitors spend their whole time in San Juan, which is a mistake.
Old San Juan The historic walled city is genuinely beautiful: narrow cobblestone streets, pastel buildings, and massive Spanish fortifications built over five centuries. El Morro and Castillo San Cristóbal, both National Historic Sites administered by the U.S. National Park Service, are the obvious anchors. Allow a full day to walk the old city properly. The forts are free for children under 15 and reasonably priced for adults.
El Yunque National Forest The only tropical rainforest in the U.S. National Forest system, about 45 minutes east of San Juan. It receives 100+ inches of rain per year, and the result is extraordinary: thick canopy, waterfalls, bamboo groves, and native wildlife including the endangered Puerto Rican parrot. La Coca Falls is right off the main road; the Angelito trail leads down to a natural swimming hole. Go on a weekday morning to beat the tour groups.
Bioluminescent Bays Puerto Rico has three bioluminescent bays — places where single-celled dinoflagellates make the water glow blue-green when disturbed. Mosquito Bay on Vieques holds the Guinness record as the world's brightest bioluminescent bay. Laguna Grande near Fajardo is more accessible from San Juan. Tours involve kayaking through a mangrove channel at night; go on a dark, moonless night for the best effect. The phenomenon is genuinely spectacular.
Vieques and Culebra The two main offshore islands offer a different pace and some of the finest beaches in the Caribbean. Vieques has Mosquito Bay and long stretches of undeveloped beach left over from former U.S. Navy use. Culebra's Flamenco Beach is a near-perfect horseshoe of white sand. Both islands are reached by ferry from Ceiba (about 1.5 hours from San Juan) or by short flight.
Ponce Puerto Rico's second city has a handsome colonial plaza, colorful fire station (now a landmark), and the Museo de Arte de Ponce — one of the finest art museums in the Caribbean, with an impressive European collection. Worth a day trip or overnight from San Juan.
The Panoramic Route A series of mountain roads running east to west across the island's central spine, passing through coffee country, rural towns, and the Toro Negro Forest Reserve. Best done over two or three days with a rental car. Most tourists never make it here, which is precisely the point.
Rincón A laid-back surf town on the western tip of the island, popular with both serious surfers and those who just want to watch the sunsets. The west coast has a different character from San Juan — quieter, less developed, more distinctly Puerto Rican.