Fortifications of the inner German border

The inner German border was a complex system of interlocking fortifications and security zones 1,381 kilometres (858 mi) long and several kilometres deep, running from the Baltic Sea to Czechoslovakia. The outer fences and walls were the most familiar and visible aspect of the system for Western visitors to the border zone, but they were merely the final obstacle for a would-be escapee from East Germany.

Source: Wikipedia — Fortifications of the inner German border (CC BY-SA 4.0)