Located 25 kilometers from the town center is this monument of probable Arab origin. Rebuilt after the 1531 earthquake, it features an interesting sculpture above the main gate, where three castles and an eagle are visible. After assuming great defensive importance, it lost its usefulness over the years, and only between 1941 and 1954 did it undergo renovations that gave it its current appearance, with two towers. It served as a prison during the Middle Ages.

Small section of a masonry defensive wall that stands back to back to modern buildings.

Located on a rise of about 70 meters, west of the monastery, Alcobaça Castle was commissioned by King Afonso Henriques in 1147, on the presumed ruins of a 6th-century fortification. Destroyed several times during the Reconquista, King Sancho ordered its reconstruction to shelter the Alcobaça monks and the population in case of attack. After suffering several seismic shocks, it ended up serving as a prison during the reign of the Philips.

It overlooks the river and, according to archaeological excavations, was inhabited during the Iron Age and early Roman occupation. Built in the 14th century as a border defense, it underwent renovations in the 17th century. Inside, there is a small museum displaying archaeological finds and remains of buildings discovered during the excavations.

A castle located in a border area that was the scene of many war campaigns. The construction of the wall, reinforced with semi-cylindrical towers, was the result of a deal between the people of Alegrete and King Dinis: the residents would build the wall, and the monarch would grant the charter. In addition to repopulating the village, Dinis built the keep and, in 1319, continued the work begun by his father, Dom Afonso III. The old town clock stood at the main gate of the old fence.

A rectangular castle with two corners formed by towers. It was built by King Dinis in the 13th century. One of the entrance gates bears the royal crown and King Manuel's coat of arms. Currently, only sections of the wall remain, some of which are integrated into buildings, such as the Porta da Conceição and the Torre da Couraça.

Castle located on top of a rocky cliff, enjoying a privileged position as a viewpoint, the exact date of its construction is unknown, but it is assumed that it was built by Mendo Rufino, during the reign of King Afonso Henriques or during the reign of King Sancho I. From the castle, currently in a precarious state of conservation, remain some turrets, a small courtyard and the Keep, inside which three records of occupation are visible, the first two of use for housing and the last of defense. It belonged to the group of castles that formed the defense line …

Built on a hill overlooking the river, human occupation of this area dates back to the Iron Age. It allowed control of the river port that connected it to the sea and protected the population from enemy attacks. A vast walled area, two towers reinforce its defenses. From its walls, one can see the plain and the series of hills leading to Monte Clérigo beach.

Located on a rocky Islet in the river Tagus, a Templar Castle warrant lift by Gualdim Pais, in the 12th century. Previously, it is believed to have existed a castro lusitano, improved by the Romans. The walls are flanked by ten towers that surround the keep and which gave the set an important defensive capabilities. Inside, there are several monumental doors that make communication between the different parts of the Castle. The access is made by river in a small boat crossing, lasting about five minutes.

Fortification with probable origins of the Castro culture, rebuilt in the medieval period, around the 12th century. Are still visible the ruins of the ancient wall around the village, which they realize its oval plant.