Sines Castle is a medieval fortress built on a cliff that has been occupied since the Paleolithic period. It was very useful for defense and is now one of the best viewpoints over the bay.
In the 14th century, the small bourgeois village of Sines demanded administrative autonomy from King Dom Pedro I in relation to Santiago do Cacém. The monarch, interested in the strategic importance of the land in protecting this coastal area from pirates, granted Sines a charter. But on one condition: the construction of a defensive fence.
The castle was built during the first half of the 15th century. Its area is relatively small, half a hectare, which may be explained by the fact that at the time the castle was built, the village already occupied an area too large to be completely surrounded.
The most famous mayor of Sines was Estêvão da Gama, father of Vasco da Gama, who carried out works on the fortress. Assuming that Estêvão already occupied this position in 1469, the probable year of the navigator's birth, this must be the birthplace of Vasco da Gama.
The castle underwent restoration work, completed in November 2008, at the same time as the inauguration of the Sines Museum and Vasco da Gama's House.
It has been a Monument of Public Interest since 1933 (decree no. 22737 of 24 June)