You could argue that the Enver Hoxha, the communist leader of Albania from 1941 to his death in 1985 was a little paranoid. He believed everyone was out to get him, which led to an extreme bunker mentality. This not only manifested itself in the 170,000 plus small concrete bunkers built across Albania but in his preparations for governing Albania in the event of an attack.

In the forests of northern Poland, just 10km from the Russian border, lie the remains of Hitler's secret war headquarters. Despite the Nazi's own attempts to blow up the site as Soviet forces approached in January 1945 many buildings are in a reasonable state of repair. Walls made of thick reinforced concrete, and its remote location, have ensured one of the more unusual remnants of the Second World War is still standing.