The Inner German Border between the former German Democratic Republic in the East and the Federal Republic of Germany in the West. Miles and miles of defences built by the Soviets and East Germans to defend the Eastern part of Germany from NATO Forces.
The patrolled defences consisted of high fences, guard towers, dog runs, raked areas to spot foot prints, minefields and scatter guns. They certainly were formidable defences too, if only they had put the defences on the right side. All the nasties were however situated to prevent movement westward, so it would seem that the designers or builders had the plans the wrong way round.