Built by the Spanish in St. Augustine to defend Florida and the Atlantic trade route, Castillo de San Marcos National Monument preserves the oldest masonry fortification in the continental United States and interprets more than 450 years of cultural intersections.
The Castillo de San Marcos is considered to be a "walk-in" park. The entrance fee applies to each individual. Tickets are not transferable and cannot be given to other guests. Adults (Age 16 and above) entrance is $15.00 and valid for 7 consecutive days. Children (age 15 and under) are admitted free of charge but must be accompanied by an adult.