Built from the bounty of the sea, Castillo de San Marcos rises in the 1670’s. Spanish masons shape blocks of coquina, sea shells cemented by their own lime, and set them with mortar made from oyster shells. Indians raft blocks from quarries on Anastasia Island. The resilient walls frustrated attackers; the rock “will not splinter,” complained an Englishman, “but will give way to cannon ball as though you would stick a knife into cheese….”