The new building's shell and roof were cast seamlessly in in-situ concrete. © Marcus Ebener

When the Berlin factory owner Ernst Marlier commissioned Paul Baumgarten to build a villa in the 'Colonie Alsen' on the Großer Wannsee in 1914-15, he had no idea what would happen to the building almost 30 years later: On 20 January 1942, the Wannsee Conference took place here, where 15 high-ranking representatives of the Nazi government planned the extermination of Europe's Jews.

However, it would be another 50 years before the site was properly used as a memorial. In the post-war period, the representative building was mainly used as a school dormitory – an uncanny idea in retrospect. In 1992, the House of the Wannsee Conference Memorial and Educational Centre was opened in the villa. The exhibition, which takes up the entire ground floor, is well worth seeing – but for a long time there was no room to expand the educational programme.

Back in 2015, Staab Architekten won the competition for a single-storey seminar building on the southern boundary of the site, between the former gardener's house and the rose garden. Nine years later, it has finally been completed. The new building is entered through a full-length atrium with a barrel-vaulted roof reminiscent of Louis Kahn's Kimbell Art Museum in Fort Worth. The space facing the old building is completely glazed. At the rear, three doors with deep reveals lead into the hall, which can be divided by folding walls into three seminar rooms of equal size. It is flanked on both sides by adjoining rooms: To the east are the sanitary facilities, to the west the chair storage and technical areas. The timber panelling around the hall acts as a parking pocket for the folding walls and also accommodates built-in furniture, sun protection, lighting and media technology.

The exterior walls and roof of the seminar building were cast seamlessly and monolithically in lightweight concrete. The building is supplied with cold and heat via geothermal boreholes and a heat pump, and the flat roof is extensively landscaped. The previously unsatisfactory catering situation on the site is also set to change in the near future: According to press reports, a café is soon to open in the neighbouring garden centre building. 

Architecture: Staab ArchitektenClient: State of Berlin, represented by BIM Berliner ImmobilienmanagementUser: Erinnern für die Zukunft - Trägerverein des Hauses der Wannsee-KonferenzLocation: Am Großen Wannsee 56–58, 14109 Berlin (DE)

Structural engineering, building physics: Bollinger + Grohmann IngenieureLandscape architecture: Reinald Eckert LandschaftsarchitektBuilding services engineering: Köster Planung, Plarewa - Ingenieurgesellschaft