Hamburg knew the bombs were coming, and so the prisoners of war and forced laborers had just half a year to build the giant flak bunker. By July 1943 it was finished. A windowless cube of reinforced concrete, with seven-foot-thick walls and an even thicker roof, it towered like a medieval castle above a park near the Elbe River. The guns protruding from its four turrets would sweep Allied bombers from the sky, the Nazis promised, while tens of thousands of citizens sheltered safely behind its impenetrable walls.
Coming in at night from the North Sea just weeks after the bunker was finished, British bombers steered for the spire of St. Nikolai in the center of the city. They dropped clouds of metallic foil strips to throw off German radar and flak gunners. Targeting crowded residential neighborhoods, the bombers ignited an unquenchable firestorm that destroyed half of Hamburg and killed more than 34,000 people. Towering walls of fire created winds so strong that people were blown into the flames. Church bells clanged furiously.
The spire of St. Nikolai, which somehow survived, stands today as a mahnmal—a memorial reminding Germany of the hell brought by the Nazis. The flak bunker is another mahnmal. But now it has a new meaning: An urban development agency (IBA Hamburg) and the municipal utility (Hamburg Energie) have transformed it from a powerful reminder of Germany’s shameful past into a hopeful vision for the future.