Island lovers, nature enthusiasts, and history buffs alike flock to San Juan’s tropical rain forest, turquoise waters, and 16th-century Spanish colonial historic district—a UNESCO World Heritage Site. The Puerto Rican capital’s proximity to El Yunque National Forest makes it easy to escape into the lush wilderness, hiking to waterfalls or soaring through the air on a zipline. If you only have time for only one epic adventure, make it a kayaking tour of Laguna Grande, where you can marvel at the natural phenomenon of millions of bioluminescent microorganisms glowing in the water after dark. And don't miss a visit to the Casa Bacardi rum distillery.