The fishing village of Peniche raised concerns about its defense from the beginning. In 1557, Don Juan III, aware of the need to strengthen the defenses north of Lisbon and after a brutal attack by French corsairs, ordered the fortification of Peniche under the direction of Don Luis de Ataide, Count of Antigua.

The impressive round tower was completed the following year, in the middle of Don Sebastian’s reign. After some interruptions, in 1589, the architect Filipo Terzo arrived in the city to continue the construction, building four bastions that initially did not provide sufficient protection. 

The fort was completed only during the reign of Don Juan IV, during the reconstruction of the kingdom’s forts and the coastal defense system. Under the leadership of Don Jerónimo de Ataide, the fortification was completed in 1645. Father Simão Falonio of the Society of Jesus and Sergeant Major Belchior Lopez de Carvalho also participated in this work. In 1671, the walled portion of the Military Plaza was completed.

Protected from the land by a platform moat, the fortress became one of the most important in the kingdom, covering an area of twenty thousand square meters. In the mid-eighteenth century, the Ataide family had their property confiscated because of their family ties to the Tavoras, persecuted by the Marquis of Pombal. As a result, the armorial stones in the Round Bastion and the coat of arms of the citadel were cut down to erase the memory of the fort’s founders.