A former World War II bunker in the St. Pauli area of Hamburg, Germany, is being transformed, in a $63-million project with five additional floors of new, vegetation-covered cultural and sports spaces and a modern hotel.

The Flak Tower IV was built with slave labor around 1942. It sheltered up to 25,000 people at a time under its 5-m-thick concrete roof during Allied air raids.

Since the 1990s, under the control of developer Matzen Immobilien, the 40-m-tall concrete block with a square footprint of 75 m per side has had various commercial and cultural uses, including a nightclub, music store and music school.

在2019年开始的工作期间，Matzen添加了五个锥形地板，由16个大型混凝土填充的钢柱支撑，在掩体墙壁上，厚度高达4.5 m。

Steelwork brackets, weighing around 5.5 metric tons each, are being attached to the bunker walls to support a 300-m-long, 5-m-wide "mountain path" wrapping around the building from ground level to the roof garden.

据Matzen发言人说，近5,000棵树，灌木，树篱和攀岩厂将增强该项目，该项目将于今年完成。