Fuerte de San Juan is a 17th-century military fort northwest of Encinasola in Huelva province, Spain, built between 1645 and 1648 to protect the frontier settlement against Portuguese incursions. Designed by engineer Rafael de Médicis, the structure features stone and brick construction with a distinctive four-pointed star bastion of sloping walls and a central cylindrical tower standing three levels high. The tower-bastion originally mounted two to three large-caliber cannons on its upper platform and included an intermediate level accessed by drawbridge over a deep well. Now integrated into the urban landscape, it stands as a preserved example of Early Modern Spanish military architecture.
