The Berlin Wall stretched over a hundred miles. It ran not only through the center of Berlin, but also wrapped around West Berlin, entirely cutting West Berlin off from the rest of East Germany.
The wall itself went through four major transformations during its 28-year history. The Berlin Wall started out as a barbed-wire fence with concrete posts, but just a few days after the first fence was placed, it was quickly replaced with a sturdier, more permanent structure made out of concrete blocks, topped with barbed wire.
The first two versions of the wall (barbed wire and concrete blocks) were replaced by the third version of the Berlin Wall in 1965. This version consisted of a concrete wall, supported by steel girders.
The fourth version of the Berlin Wall, constructed from 1975 to 1980, was the most complicated and thorough. It consisted of concrete slabs reaching nearly 12-feet high (3.6 m) and 4-feet wide (1.2 m), plus it had a smooth pipe running across the top to hinder people from scaling the Wall.
The Berlin Wall began as a simple fence but evolved over time into a complex deterrent system. By the time the Berlin Wall fell in 1989, there was a 300-foot No-Man's-Land, an additional inner wall, soldiers patrolling with dogs, a raked ground that showed footprints, anti-vehicle trenches, electric fences, massive light systems, watchtowers, bunkers, and minefields.
Although most of the border between East and West consisted of layers of preventative measures, there were little more than a handful of official openings along the Berlin Wall. These openings, called checkpoints, were for the infrequent use of officials and others with special permission to cross the border. The most famous of these was Checkpoint Charlie, located on the border between East and West Berlin at Friedrichstrasse. Checkpoint Charlie was the main access point for Allied personnel and Westerners to cross the border. (Soon after the Berlin Wall was built, Checkpoint Charlie became an icon of the Cold War and was frequently featured in movies and books set during this time period.)