Ready for an island getaway? Puerto Rico, a commonwealth of the United States, offers an exciting blend of old and new, from the walled, colonial city of Old San Juan to modern, luxurious resorts. Outside the capital of San Juan, visitors can explore the El Yunque Rainforest or swim in the bioluminescent bays, where colonies of dinoflagellates make the ocean glow. At Rio Camuy Cave Park, you can explore sinkholes and underground rivers. Those searching for real seclusion can fly to Vieques, a relatively unexplored island with pristine beaches ideal for snorkelling.