The National Archive of Torre do Tombo (Portuguese: Arquivo National da Torre do Tombo, [ɐɾˈkivu nɐsjuˈnaɫ dɐ ˈtoʁɨ ðu ˈtõbu]) is the Portuguese national archive established in 1378, located in center-north Lisbon, and renamed the Instituto dos Arquivos Nacionais (Institute of the National Archives) in 2009.
The archive is one of the oldest institutions in Portugal, since its installation in one of the towers of the castle in Lisbon, occurring during the reign of Ferdinand I, and possibly in 1378 (the date of the oldest testimonal). The archive served as the King's and nobilities' reference, with documents supporting the administration of the kingdom and overseas territoies, and documenting the relationships between the State and foreign kingdoms.
More information on the Wikipedia page 
The website, in Portuguese, is