A 300-acre park here preserves a coquina shell watchtower erected in 1742 in the wake of the first British siege, as an outpost of Castillo de San Marcos. The tower replaced a wooden watchtower overlooking Matanzas Inlet that had been guarded by Spanish soldiers since 1569. Stop at the visitor's center to see a short film chronicling the fort's turbulent history, then board a ferry across the river to see the site of the fort.