While the El Morro fortress protected the entrance to San Juan's harbor, the Castillo de San Cristobal (St. Christopher's Castle), built on high ground 150 feet above sea level, protected the city from enemy land approaches from the east.
The castle is now part of the U.S. park system and has rangers on site to answer questions and give talks about the castle and its history. I have a Golden Eagle Passport which was honored with a discounted admission to the castle.
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