TIME has published photographer Don McCullin’s lost negatives that he shot of the building of the Berlin Wall in August 1961. These images of Berliners in the Western zone peeking through to their friends in the East serve as a striking complement to the more familiar images of reunification and the fall of the wall almost thirty years later. It’s difficult to imagine the cultural and psychological effects of physically dividing a major metropolis. Old streets dating to the 18th century just ended with a wall, U-Bahn tunnels were closed off, water and electricity flowed on separate grids, and of course, families were broken too. McCullin’s photos show the earliest stage of the wall’s construction. Soon the German Democratic Republic would build a second wall behind the first. Between the two walls would lie a no-man’s-land guarded by barbed wire and machine gun towers. Some sections of the wall remain today, and paved into the now unified roads and sidewalks is a narrow brick path that marks where the wall once stood — the “Mauerweg.” There is no corresponding monument to Germany’s divided consciousness, perhaps because it’s still an open wound.