San Juan National Historic Site

San Juan's Spanish colonial fortifications are the oldest European constructions under the U.S. flag: El Morro, begun in 1539, and San Cristobal, the largest fortress Spain ever built in the New World, guarding a walled city that Spain held for nearly 400 years. Together with La Fortaleza they form a World Heritage Site.

Explore tunnels, sentry boxes, and dungeons, and join locals flying kites on El Morro's great lawn. For a challenge, walk from El Morro through the old city along the city walls to San Cristobal, the full defensive system on foot.