El Morro, which sits within the San Juan National Historic Site, juts out of San Juan harbor and beckons to cruise ships. Construction of the hulking, six-story fortress started in 1539.

Kayaking in the Vieques Bioluminescent Mosquito Bay at night, ziplining through the rainforest, hiking to waterfalls, and exploring El Morro Fort are perfect activities for adventurous travelers.

The cats, which have long been a tourist attraction, are both beloved and reviled by those who visit and live in Old San Juan, where the 16th-century fortress known as “El Morro” is located.

Both the Fort San Cristóbal and El Morro dominate the San Juan Harbor. You should plan to stop by San Cristóbal on the day you visit El Morro, especially considering that you can pay one fee for ...