Ilha do Presídio, also known as Ilha das Pedras Brancas or Ilha da Pólvora, housed the fourth gunpowder house in Porto Alegre. Its construction began in 1857 and was completed in 1860. The magazine built there met the demands of the city and the province and was used until the 1930s by the military. In 1940, the space began to be managed by the State, which installed an animal research laboratory there between 1947 and 1948. Located on Lake Guaíba, in the 1950s the island was adapted to function as a maximum security prison, receiving young people accused of petty crimes, minors and the mentally ill.

With the outbreak of the civil-military coup, in 1964, the Island is transformed into a detention center for the repressive apparatus, where opponents of the regime are sent.

In the 1970s, dozens of young militants from student movements and clandestine organizations to resist the dictatorship were detained on Ilha do Presídio. Between 1965 and 1973, more than 100 citizens were imprisoned there for political reasons.

The Island has unique environmental and landscape characteristics. It differs from the other islands of Lake Guaíba, being part of a set of crystalline terrains that testify to the geological evolution of this region of the State, the hydrography and its current relief. Its natural beauty contrasts with the solidity of the architecture of its buildings, related to military use and social exclusion.

The architectural complex of Ilha do Presídio has two main buildings: the Guarda Building and the Prison Building. The buildings on the Island, which went through constructive and destructive processes, as well as the vestiges of different underground occupations, have significant archaeological value. Furthermore, it is possible that the space was occupied by pre-colonial populations. Because of this relevant archaeological potential, Ilha do Presídio was registered as a Historic Archaeological Site with IPHAN. At IPHAE, Ilha do Presídio is inscribed in the Historic Tombo Book and also in the Archaeological, Ethnographic and Landscape Tombo Book.