Located in Poça beach, in the parish of São João do Estoril with a privileged views over the sea, São Pedro Fort, also known as the Old Fort, was one of a series of fortresses built during the reign of King João IV between 1642 and 1648 and intended to form a defensive line between São Julião da Barra and Cabo da Roca. According to an inscription on the fortress gateway, its construction began in April 1642 and was completed the following year.
Rectangular in design, the main body of the fortress housed the lodgings arranged around a courtyard and covered by a terrace. The adjoining area housed the battery, an elongated structure. These buildings were surrounded by an outer irregularly-shaped parapet, which formed a first defensive barrier.
Today, the structure of São Pedro Fort has been altered. In fact, this fortress resembled the fortification of São Teodósio, albeit larger in size. After it was decommissioned in the 19th century, São Pedro Fort had various owners, with different uses at different times. In 1954 it was turned into tea house, and from 1957 was privately leased, first as a restaurant and then as a nightclub.