Bastions

Originating in Italy in the 15th century, the particular star-shaped design of the Castillo de San Marcos is a result of architecture adapting to technology.

The change in warfare brought about by black powder weapons created new types of defensive structures adapted both to withstand or avoid the impact of cannon projectiles and to effectively mount cannons to repel any attackers. Of the major architectural variations, the "bastion system," named for the projecting diamond or angle shaped formations added onto the fort walls, was the most commonly and effectively used.

The distinctive star shape of this castillo, and other forts like it, was not accidental. This is an architectural style known as a Vauban fortification. This design was the result of careful study and the application of geometric principles. The purpose of the fort’s shape is to eliminate any blind spots or dead zones from which an enemy could approach the fort or find cover. This shape also created interlocking fields of fire so that there was no direction from which multiple cannons could not fire on the enemy. In order to accomplish this, the engineers designing the fort needed to be well versed in geometry or the result could be disastrous for the defenders of the fort.

St. Augustine was in luck. Ignacio Daza, the engineer who designed the Castillo de San Marcos, had studied up on his geometry ahead of time. One of the oldest branches of mathematics, geometry is concerned with properties of space, such as the shape, size, and relative position of figures. Although it was originally developed to model the physical world, geometry can be applied to almost all sciences plus art, architecture, and any other activity related to graphics. As such, geometry has played a vital role in the history and development of this Vauban style of fortress architecture.