Strategically located at the top of the mountain of Montjuïc, the castle, which bears the same name, is an imposing defensive construction that follows the model of star-shaped fortifications. Its current appearance is due to the reformations carried out on the old installations by the military engineer, Juan Martín Cermeño, during the 18th century.

But, beyond its architecture, Montjuic Castle has been the scene of numerous bloody episodes and acts of repression throughout its 400 year history. Currently, the site is the property of the city and has become a symbol of Barcelona.

The origins of the castle date back to 1640, during the Catalan Revolt (the Guerra dels Segadors), when a small fort was built around an ancient watchtower. This was the beginning of the militarisation of the mountain, something which marked its history until the middle of the 20th century.

This small initial fortification was completely renovated and modernised by Juan Martín Cermeño. After the war of the Spanish Succession (1701-1714), ownership of the castle passed to the monarchy and a permanent garrison was established. Along with the Citadel, Montjuïc became the guardian of the city of Barcelona.

The renovation led to the demolition of the original fort and the construction of new buildings on an irregular trapezoidal plan adapted to the topography of the mountain, with four bastions at the ends and a covered perimeter path. Cermeño completed the "modernisation" of the facilities with the provision of toilets and water tanks and ordered the construction of the moat.

Throughout the 19th century, the castle once again had a military importance in the repression of insurrectionist movements in the city. Up to 3 times (1842-1843 and 1856) Barcelona was bombarded from the fortress, which was also used to imprison unionists, anarchists and revolutionaries, as well as during the Setmana Tràgica (Tragic Week) of 1909. With the Spanish Civil War the Republican government used the area for similar purposes. Later, the castle instead became a War Memorial to the victors, a military prison and the scene of councils of war (its most political significance was as the site of execution of the president, Lluís Companys).

It became a military museum in 1963. Finally, the Castle passed to municipal ownership in 2007, definitively closing the doors of the museum and taking back the space for the city.