Located in Elvas, the Graça or Lippe Fort is a perfect example of 18th century military architecture. Many historians consider it to be one of the most powerful fortresses in the world. Its good strategic position be-came evident during the War of Restoration, when Spanish troops occupied the site during the siege of the city of Elvas in 1658, which preceded the Battle of the Lines of Elvas on 14 January 1659. Made up of three bodies – the outer works, the main body and the central redoubt – the Graça Fort is an example of Vauban-type military architecture. The central body is composed of four bulwarks, with the main door in the middle of the southern curtain, of a unique beauty. In 1856, when the war was going on in other directions, a cor-rectional facility was created in this space. And in 1894 a disciplinary warehouse where several political prisoners were held from the 1st Republic until 1974. The Graça Fort has been classified as a National Mon-ument since 1910. And as a World Heritage Site since 2012.