What few people know about, however, is the story behind the almost eight-decade-old flak bunker: it’s a time that recalls the darkest chapter in German history. Built in 1942 in only 300 days by forced laborers, today the St. Pauli Bunker is a memorial to the victims of the Nazi regime and the Second World War. In the course of the reconstruction work, hidden traces from this period have constantly been appearing—directions or the designated entrance to the “Wehrmacht Hospital” are but a few.

To make the history of the bunker both experienceable and understandable as an integral part of the city and district’s culture, while also connecting it with the current needs of residents and occupants, non-profit association Hilldegarden e.V. created the AG Mahn- und Gedenkstätte Flakbunker IV. This is an investment project that combines a culture of remembrance with social and ecological involvement. For the first time, there will be a place in the St. Pauli Bunker where its history and the memory of the Nazi regime’s victims will be commemorated. The research and development for this exhibition concept is done in close cooperation with the office of gwf-ausstellungen – Konzept & Gestaltung, which previously carried out the planning, design, and curation for the Neuengamme Concentration Camp Memorial.

Neighborhood initiative Hilldegarden e.V. is one of the driving forces behind the concept, the realization of further structural development, and use for the St. Pauli Bunker. It was established with the aim of creating a place of community, recreation, and a completely new style of urban nature. Prof. Dr. Thomas Matzen was immediately convinced when he saw the architects’ idea: an extraordinary city garden on the roof of the former high-rise bunker that combines the previous “media bunker” character and the residents’ desire for a natural oasis with self-managed urban gardening spaces. In addition, rooms for exhibitions and concerts as well as extraordinary accommodation for artists and creative types will be established according to the architecture firm’s plans.

The spectacular highlight of the expansion is the publicly accessible natural oasis. As a place for people to cross paths, it facilitates interaction and pleasure above the city skyline. The walk along the green “mountain path” around the outside of bunker is an outstanding experience in its own right. The evergreen park is the work of the Lorenz von Ehren nursery. It won’t be long before the first trees take root at a height of over 50 meters. Hilldegarden e.V. makes the interactive garden experience possible with raised beds and spaces for urban gardening.

This interplay of architecture, history, and active citizen participation is already arousing great curiosity both at home and abroad.

After the end of the war, the Allies planned to blow up the many high-rise bunkers in the city as part of the denazification initiative, including the high-rise bunker in Feldstrasse and today’s “energy bunker” in Wilhelmsburg. Due to the massive construction that included a wall or ceiling thickness of up to 3.8 meters on a surface area of 75 x 75 meters, however, the St. Pauli bunker was not blown up: to do so would have endangered the adjacent and even more distant residential areas. Due to the great housing shortage toward the end of the war, the former bunker also offered accommodation to many of the local bombed-out residents.

Soon, the St. Pauli Bunker—today a protected monument—found a new function in the quarter. By accommodating companies from the worlds of art and culture as well as music clubs and events, the wartime relic was to be transformed into a lively creative center.

The Hilldegarden association has founded the Arbeitsgruppe Gedenkstätte (“Memorial Working Group”) and more as part of a broad investment project. The memorial is intended to pay tribute to the bunker and make its history accessible to the public. Further information can be found on the Hilldegarden e.V. website.

“The consequences of the climate crisis have also reached Germany and Europe,” said German Environment Minister Steffi Lemke (Greens) at the recent presentation of the action plan. “That’s why it is necessary that we take care of the protection of the population in changing climate times.” The heat-related death toll is too high, she said, and the preventive measures taken so far are too few. In 2022 alone, more than 4,500 heat-related deaths occurred, according to the Robert Koch Institute. The UN World Climate Report calls for cities to adapt their infrastructure to climate change. This is because the statistics show that the number of heat days with temperatures above 30 degrees continues to increase. It is well known that more and more air conditioning systems with their high energy consumption are not the solution, but part of the problem. But what can help against urban heat islands?

Climate scientists agree on how to keep our cities livable in the future: More greenery, more shaded areas – and less soil sealing. This is because increasing building development is blatantly heating up metropolises. In Hamburg, too, land consumption continues apace; according to current figures, around 39 percent of the city’s area is built on, concreted over and asphalted.

From a climate perspective, it is crucial to compensate for this enormous loss of land with new vegetation areas, says Marco Schmidt of the TU Berlin. The expert has installed about 80 sensors in the bunker addition and is analyzing the effect of the greening on the building and the microclimate over a 5-year period. The survey is sponsored by the German Federal Ministry for the Environment, among others. Precise data and figures on the effects of green roofs and facades are scarce and have so far mostly been based on model calculations. The bunker values collected by the TU Berlin will be made available to projects worldwide in order to optimize building planting in the future.

Experts already agree that green roofs and facades promote climate neutrality and act like natural air conditioning systems. They cool in summer and insulate in winter. They help save energy, improve the microclimate and air quality, and provide necessary space for more biodiversity.

Apart from the mountain path, about 80% of the planned bunker planting has currently been planted, in addition to supplementary perennial plantings, among others. Many of the woody plants are now up to 25 years old. They were combined with younger woody plants to ensure a staggered appearance and a particularly long-lasting greenery. A mixture of conifers and deciduous shrubs is used to achieve a seasonally varied appearance.

From a horticultural point of view, young plants are generally recommended for facade greening, as they grow better in the new location and develop more advantageously there in the long term. The climbing plants on the bunker still need time to grow and will predominantly overgrow the facade of the extension in the future. The parapets will then only be visible in isolated sections where greenery is not possible for reasons of fire protection or maintenance. The existing building will deliberately remain unchanged in consultation with the authorities responsible for the preservation of historical monuments.

A number of animals are already enlivening the new public urban garden. Birds such as robins are obviously not bothered by the work still in progress. Insects and beetles have also discovered the space above the roofs of Hamburg.

The planned irrigation of the 4,700 trees and groves is also sustainable: A temperature- and humidity-controlled irrigation system primarily uses the rainwater that accumulates. The so-called “sponge city principle” is crucial for protecting our cities from water floods. This is because heavy rainfall events are also becoming more frequent in Germany: In Hamburg, the A7 highway and the Elbe Tunnel were recently affected by flooding caused by an exceptionally high amount of precipitation. Green roofs can mitigate this risk; they store precipitation and cool buildings through evaporation. On the bunker, precipitation is first retained by a cascade system on each level through different storage capacities and then transferred to the next level. This solution at the bunker can relieve the urban sewers of about 80 percent of the water volume that would otherwise be generated.

As a result, the pioneering landscape architecture project with its 4,700 plants selected to suit their location will become one of Germany’s most impressive urban gardens, pointing the way to the future and encouraging planners to design climate-adapted cities.

More on the topic at Spiegel online:

https://www.youtube.com/watch?v=rgqL2JOjSIY

Text/Photos: Frank Schulze Kommunikation