Sometimes referred to as the Caribbean National Forest, the El Yunque National Rainforest, or simply El Yunque, this lush expanse is the only tropical forest in the U.S. National Forest System. It's also a particular favorite for vacationers who like to hike — but even if nature really isn't your thing, travelers urge you to make the trip just 35 miles east of San Juan. Remember to wear layers that can get wet — the site receives more than 100 billion gallons of precipitation annually — and pack a water-resistant camera to capture some of the area's splendor. Keep your ears peeled in the evenings, when Puerto Rico's tiny coquí tree frogs begin their serenade.

The forest has 13 well-marked hiking trails that range in difficulty. The two most popular, La Mina & Big Tree Trail, are a combined two-hour hike that snakes by La Mina River and ends around La Mina Falls. 

Travelers agree that El Yunque is too much to handle in one day; many choose to camp or find accommodations in the area. You can obtain a free permit (before 3 p.m. each day) to camp on El Yunque's premises, but facilities are few and far between. Many hotels in San Juan offer day trips or excursions to the rainforest, so be sure to inquire with your concierge.

Entering the forest is free, but there's a modest admission charge into El Portal visitor center or to arrange an overnight tour of the forest. Visit El Yunque's official website for further details.