El Yunque National Forest
In the verdant Sierra de Luquillo mountain range about a half-hour east of San Juan, the 28,000-acre tropical forest of El Yunque is one of the United States' most diverse preserves. More than 240 species of trees and plants, as well as more than 50 different bird varieties, make their home here. The preserve is crisscrossed with hiking tails of varying degrees of difficulty; many of them skirt waterfalls and natural swimming pools that visitors are welcome to plunge into. There are lots of tour outfits leading guided treks in the forest, but it's just as easy to navigate the park on your own, in a car or on foot; just pick up one of the well-marked maps at the tourism center at the park's entrance.
Tip: On the way back to San Juan, stop at the Las Vegas restaurant (Rte. 191, Km 1.3, Río Grande; 787/809-6586), which is just down the road from the main entrance. Despite its cheesy Amazonesque décor, the restaurant offers a sophisticated menu of modernized Puerto Rican food, like curry-spiced crab turnover served with plantains.
Open daily, 7:30 a.m.–6 p.m.; $3 entry