For most of its recorded life the hill was unremarkable in the best sense. It was called Walpurgis Mountain until the fifteenth century, and the Saale valley around it holds traces of settlement reaching back to the Middle Palaeolithic. Three quarries have cut sandstone from its flanks since the Middle Ages, most of it going into the foundations of local houses; the scars are still visible. Terraces were built on the sunny southern slope for vines, though winemaking here faded in the seventeenth century. A trade route crossed the top, known as the Green Street and later as the Gothic Street because it ran toward Friedenstein Castle in Gotha. Then, in 1897, the porcelain makers of Kahla found kaolin-bearing sand inside the hill and began digging. By the time they were finished, twenty kilometres of galleries ran through the sandstone.

The acronym stood for Reichsmarschall Hermann Göring, and it is the only name most of the people who died here ever knew for the operation. From April 1944 the porcelain company's galleries were driven out to thirty kilometres to house an assembly line the Allies could not bomb. More than twelve thousand forced labourers did that work — deportees from Italy and from across occupied Eastern Europe — alongside some three thousand skilled workers, housed in a ring of camps around the mountain. They cut rock, poured concrete, and hauled spoil in conditions that killed by accident, rockfall, exhaustion, disease, cold and beating. Every year around 8 May, the villages beneath the hill hold ceremonies for the roughly two thousand who did not survive it. Former forced labourers travel from abroad to attend, a tradition that has outlasted almost everyone who began it.

The problem with building aircraft inside a mountain is getting them out and into the air. The solution at Kahla was audacious and slightly deranged: lay a runway across the flat summit, and haul finished airframes up the flank on an inclined railway built into the hillside from the tunnel mouth. It worked. The first Me 262 lifted off the top of the Walpersberg on 21 February 1945. American troops reached the site on 12 and 13 April and liberated it, seven weeks later. In that window, somewhere between twenty and thirty completed aircraft left the hill — a figure that should be set against thirty kilometres of tunnel, fifteen thousand workers, and two thousand graves. As a piece of engineering it was remarkable. As a use of human lives it was, by any measure the arithmetic allows, a catastrophe.

The Soviets destroyed much of the structure after the war, and the surviving galleries went on to have an oddly domestic second life: through the 1950s they held a fruit and vegetable warehouse, and from the 1960s a geological research enterprise stored drill cores in them. From 1974 until 1989 the hill was East German defence depot KL-22, packed with ammunition, weapons and military stores. The Bundeswehr kept it going until 1997, when running costs closed it for good. Two museums now tell the story: an exhibition at the Kahla town museum, and the documentation centre run by the Geschichts- und Forschungsverein Walpersberg in Großeutersdorf. Both cover the same ground — the construction, the camps, the forced labour, the liberation — and the association leads regular guided tours on the hill itself, which is the only way to stand where the runway was and understand what is underneath it.