Fort Matanzas located at 8635 A1A South in St. Augustine. Pick up tickets to the ferry at the visitor center. The center situated on 100 acres includes a one-half mile nature trail. Plaques that surround the visitors center give a detailed history.
The Spanish built Fort Matanzas between 1740 and 1742 . The land that surrounds the fort is Rattlesnake Island home to endangered species . Fish and crabs in the salt marsh. Seven soldiers stationed at the fort at all times. Two Spanish 8‑Pound Iron Gun Cannons delivered to Fort Matanzas in 1793 and left when the Spanish abandoned the fort in 1821. The fort left abandoned for 100 years. Restoration took place between the 1920s and 1960s. Photographs are allowed and you can climb to the top if you wish.
I recommend visiting the fort and enjoyed the tour immensely; the park rangers are well versed. Entrance to the park is free, hours of operation on the website.