For more than 300 years an imposing structure has protected St. Augustine’s harbor. Built under Spanish rule, the Castillo de San Marcos stands as the oldest masonry fort in the continental United States! Come learn of the fort’s storied history and the firm foundations upon which it is built. Kids will construct their own miniature Castillo. Each free program runs from 11:00 a.m. to 12:00 p.m. and is designed for children ages 4 to 8 and their families.