The first reference dates from 1390 in an order from D. João I for the construction of a coastal watchtower. However, there is news of a Roman temple dedicated to Neptune on the same site.
Over the centuries, it has undergone several expansion and remodeling works.
In the XNUMXth century, after having been a prison and a holiday home for the royal family, the fort was offered to D. Amélia to install a sanatorium there, which, after the reduction in the number of tuberculosis patients, was transformed into the Orthopedic Hospital of Santiago do Outão. which still remains today.