The Castillo was built "to protect and defend Spain's claims in the New World. Though caught in the whirlwinds of colonial warfare and intrigue, it was never defeated in battle. Its scarred walls still stand witness to over 330 years of history and culture."
The Castillo de San Marcos is a very popular destination for school field trips. Ranger-led educational tours are no longer provided. Schools which perform a self-guided field trip are eligible for and may request a waiver of the admission fees.
The Castillo de San Marcos is open to the public from 8:45am to 5:15pm every day of the year except Thanksgiving (fourth Thursday in November) and Christmas Day (December 25). The ticket booth closes at 4:45pm.