Coming from the east around 1980, you met the border in layers. First the Sperrzone, five kilometres deep, where residents needed permits to come and go, could not visit the next village, and lived under curfew. Then the signal fence: 1,185 kilometres of expanded metal, two metres high, wired to raise an alarm the instant it was touched or cut. Beyond it lay the Schutzstreifen, watched from towers and from around a thousand two-man bunkers whose entrances faced east, hiding the guards from Western eyes. Then the Kolonnenweg, then the raked control strips, kept as bare earth for one reason: footprints. Then the fence itself, up to four metres of mesh with holes too small for fingers and edges sharp enough to open a hand, its lower panels buried against tunnelling. Fifty thousand Border Troops served all this. On the Western side there was nothing at all — just warning signs, and civilians free to stand on the line.

From 1970 the outer fence carried about 60,000 SM-70s: horn-shaped charges bolted to the mesh and wired to tripwires. Touch the wire and the horn fired a cone of shrapnel along the fence, lethal to roughly twenty metres. They were not aimed at anyone in particular. They simply waited. Behind them lay some 1.3 million landmines. An East German army study of attempts between January 1974 and November 1979 set out the arithmetic: of 4,956 people who tried to cross, 229 got over the fence — fewer than one in twenty. Forty-eight were stopped by mines and forty-three by the SM-70s, and in official language "stopped" covered killed as well as injured. International condemnation eventually did what protest could not, and the last SM-70 came off by the end of 1984. The mines took longer: after reunification 34,000 were still unaccounted for, and clearance ran until the end of 1995.

Michael Gartenschläger, an East German political prisoner who had got out to the West, had a specific quarrel with the SM-70: the GDR denied the devices existed. On 30 March 1976, near Büchen, he crossed to the fence, unbolted a live one, carried it back and handed it to West German authorities. On 23 April, against everyone's advice, he did it again. The second theft made the newspapers, which told the border guards exactly where to wait. A 29-man detachment prepared concealed firing positions. On 1 May 1976, as Gartenschläger climbed his ladder for the third time, a searchlight caught him and a burst of automatic fire knocked him off it. No warning was given, no surrender demanded. The Stasi's own report recorded that he had been "liquidated by security forces of the GDR."

Roughly a thousand people are thought to have died on this border, and estimates have crept upward as East German records surfaced — up to about 1,100 by 2009. The GDR kept the count secret, so most of the dead reached us without names. A few did not. Kurt Lichtenstein, a journalist with the Westfälische Rundschau, was shot near the village of Zicherie on 13 October 1961 for trying to talk to East German farm workers across the line; students from Braunschweig put up a sign at the spot. Heinz-Josef Große died in 1982, and for years afterwards people gathered on the Western side to remember him. The border emptied the countryside behind it, too. In an operation the state codenamed Aktion Ungeziefer — Operation Vermin, the word a government chose for its own citizens — more than 8,300 people were forced from their homes along the line. Another 3,000 saw it coming and fled.

In December 1989, a month after the border opened, conservationists from both Germanys sat down with an idea. Forty years of exclusion had done something nobody planned: the strip nobody could farm, build on or walk through had quietly become a refuge. They proposed a Grünes Band, a Green Belt following the scar of the frontier from the Baltic to the Czech border. The Bundestag voted unanimously to protect it in December 2004, folding it into a European Green Belt that traces all 6,800 kilometres of the old Iron Curtain. The German section now links 160 nature parks, 150 protected flora-and-fauna sites, three UNESCO biosphere reserves and the Harz Mountains National Park. Wildcats live there, and black storks, otters and orchids that have vanished elsewhere. More than half of Europe's 25,000 red kites nest along the old line. The border was abandoned on 1 July 1990, forty-five years to the day after it was drawn.