El Cielo, aptly named "Heaven" in Spanish, is a secluded sandbar approximately 2 miles off Cozumel's coast, renowned for its silky white sands and crystal-clear turquoise waters. Accessible only by boat, this idyllic spot has become a favorite among snorkelers and marine life enthusiasts. Beneath its shallow waters, visitors can observe a vibrant array of sea stars, commonly known as starfish, gracefully adorning the sandy floor. The area is also frequented by gentle stingrays and, occasionally, sea turtles, offering a serene glimpse into Cozumel's rich underwater ecosystem.

The Library of Congress is the largest library in the world, and its three buildings — the Thomas Jefferson, James Madison Memorial, and John Adams — are well worth exploring. Free tours show off the architecture and highlight the rare collections, while exhibitions, gallery talks, concerts, and lectures give visitors plenty to see and do.

The United States Capitol dominates the eastern end of the National Mall on Capitol Hill — its dome, completed during the Civil War, is hard to miss. The Capitol is the seat of the United States Congress, and it has been a center of American politics since 1800. Inside, the Visitor Center walks you through its history, shows off its art collection, and explains how the legislative branch works. Free guided tours are available, but booking ahead is a good idea — lines can get long, especially in peak season.