As early as 1598, they dug enough to build a gunpowder storage magazine. But they had neither the manpower, the engineering skills nor the tools to excavate enough for a large structure. Finally, in 1671 large-scale quarrying began in the stone pits. Coquina rock is relatively soft and easy to cut while in the ground and hardens when exposed to air. The Spanish learned to waterproof the stone walls by coating them with plaster and paint.
Coquina rock has a unique feature that made it ideal for a fort.
When besieging ships bombarded the Castillo, the walls simply absorbed the cannon balls. You can expect to see different species of herons including Great Blue Heron, Little Blue Heron, Tricolored Heron and Green Heron. Snowy and Great Egrets can be spotted, as well as the White Ibis, Wood Stork and Roseate Spoonbill. If you're interested in raptors, our year round residents can be seen best from late in the morning throughout the day. Look for the Red-shouldered Hawk, Bald Eagle and Osprey.