The appearance of modern Belfast is strongly influenced by the Defensive-Planning of the British army, the motorway, parks or industrial areas were planned to segregate catholic and protestant communities in an maximum natural way. An excessive amount of Defensive Architecture were additionally installed around critical zones during the beginning of the North Ireland conflict in the 70th, the so-called peace lines; a mix of walls, gates and fences. The most walls were build in the peak of the so-called »Troubles« in 90th, but one third of those barriers were build after the ceasefires and the end of the conflict in ‘96. The peace lines and the excessive amount of private and constitutional Defensive Architecture such as military barbed wire, video observation, solid walls, anti climb obstacles, gates with vehicle or pedestrian access creates an odd atmosphere in the city. The Defensive Architecture is till nowadays not just a practical barrier but a psychological.