[Ft. Marion-St. Augustine & Harbor, FL]

Completed in 1695, Fort Marion (now Castillo de San Marcos) is the oldest surviving masonry fort in the continental U.S. Engineer Ignazio Daza followed standards for building defensive structures that would withstand cannon projectiles and maximize cannon mounts to repel attackers. The bastion was built to defend St. Augustine against British attack. The coquina shell walls did not splinter into projectiles under cannon fire and when mixed with aggregate, absorbed cannon balls.