21107 Hamburg-Wilhelmsburg: The former flak bunker in Wilhelmsburg has become a symbol of the climate protection concept Renewable Wilhelmsburg. The monument, which has been virtually unused since the end of the war, was refurbished as part of the IBA Hamburg and converted into a renewable power plant with large-scale heat storage. The energy storage facility has a volume of 2,000 cubic metres, which corresponds to 2,000,000 litres. It supplies the 120-hectare Reiherstieg district with climate-friendly heat and feeds renewable electricity into the Hamburg distribution grid.