The Calulo Fortress was built by the Portuguese colonial authorities at the end of the 19th century, as an instrument of defense against the strong resistance of local natives to the occupation.
This resistance had particular relevance from 1895 onwards, under the command of Soba do Libolo (Golungo). The construction of the Fortress was started in 1897 by Lieutenant Pais Brandão.
In July 1917 there was a large popular uprising against the colonial forces, with the Fortress serving as a refuge for the occupying forces.
The Portuguese military occupation of Libolo would only be consolidated in 1932, and at that time the phrase “1917 - Homage to the fighters of the Libolo revolt” was engraved on a stone in the Cassalasala area. This phrase is recognized as a true tribute to the resistance of the people of Libolo.
The Fortress has always been an icon of the region, both in the colonial period and after Angola's independence, having always been the last defensive stronghold of the forces holding local power.