By 1957 the commandant-in-chief of the Military Region of Northern Portugal, based in Porto city, conducted a study in order to adapt the Castle of São João da Foz, at Foz do Douro parish, for a museum. However, the idea was definitively abandoned by 1970, due to the high cost of the adaptation of the building. A new location was identified in 1977, in a building in the "Rua do Heroísmo", where the delegation of the former secret police PIDE/DGS used to be located between the 1940s up to 1974.