09/28/2026
Castillo de San Marcos
Let's talk about the parts of the 'old fort' that you may recognize but don't know about them.
The Castillo was constructed to defend the Spanish stronghold of St Augustine. It is a star shaped structure that has four diamond-shaped bastions on each corner and a ravelin at it's 'mouth', built on and surrounded by 3 different levels, all designed to assist in protecting the fort itself.
BASTIONS: diamond shape corners that . . eliminate blind spots, create deadly crossfire from atop, and are packed solid with coquina and rubble to support the weight of cannons on top--walls up to 14 feet thick.
GARITAS: curved sentry boxes projecting from the corners of the bastions, designed to hold a lookout guard, allowing a 180 degree view while shielding them from enemy fire.
CURTAIN WALLS: the walls connecting the bastions, mounted with embrasures (openings) on top to allow cannons to be rolled up and into opening.
RAVELIN: triangular outer work to shield the only entrance from enemy fire. This current ravelin was built (replacing the old) in the mid 1700's but never completed. 😯
GUN DECK: used for the obvious. . .holding weapons used for defense. While it can be confusing, cannons are also called guns. BIG guns lol
The Spanish ended up lowering the east wall, anticipating that most attacks would come from the ocean. Therefore it is the only wall with no embrasures, as by having a low open wall, the amount of guns would not be limited.
CANNONS: The Castillo used cannons made out of bronze or iron and of many sizes. The largest ones had a target range up to 3 and 1/2 miles!
The fort has many different ground levels surrounding it, all having a definitive purpose.
GLACIS: a hill leading up to the closer areas of the fort. This provided essential protection of the fort from enemy fire as well as providing an open view of the surrounding area to any enemy intrusions.
COVERED WAY: This is the mid level section of surrounding areas, allowing the soldiers to move about the grounds without being detected and also providing their protection.
MOAT: the lowest level that the fort itself is laid out on/in. NO, the moat was never intended to have water in it. It was used as a pen for domestic animals during times of siege. But yes it did have water between the early 1930's until 1996, when the damage caused by such water was realized, so the moat was drained. It is now as it was in the beginning (dry), however to stabilize the fort after the damage sustained, several feet of earthen material was added. Thus the moat now lies higher than it was originally.
WATER BATTERY: the east side of the moat level was 'filled in' several feet by the US Army in the 1840's, thus developing a water battery, design to mount cannons to be closer to enemy ships. The HOT SHOT furnace was also built then in the water battery, designed to heat cannon balls before shooting them at wooden ships, thus setting them ablaze in addition to cannon damage.
Note: as the water battery is described as filling in the moat area to create a higher mount, it may seem confusing if you are walking the area, as it is very close with the current level of the moat. But if read above about the moat, it used to actually be several feet lower.
This content message is a very brief overview, designed to make you familiar with different areas and parts of the Castillo de San Marcos. It is not an exhaustive list nor description. There will be more posts in the future going into some more details of several features.
Hope you enjoyed! Take a walk around the Castillo and observe first hand these historical details.
