The GSW building is an important chunk of the new Berlin. It is on Kochstraße, part of Friedrichstadt, the Baroque inner city, just south of the great streets and squares of the centre. The whole area was bombed to bits, then languished in a limbo caused by the Wall. A solitary tower stood well back from the road (which was to be widened). The architects were asked to make a new headquarters for Berlin’s largest housing association, and seized the opportunity to try to return the site into conversation with the remaining fragments of the eighteenth- and nineteenth-century cityscape. In addition to the original 17 storey head-quarters, there is a new curved 22-storey block, no more than 11.5m wide, which allows for natural light and natural ventilation. With its yellow, green and blue aluminum drum on top of the baguette, this is a distinctive and environmentally friendly building. A low building on Kochstraße returns the street to decency; new small public spaces and mixed uses make the place an important constituent of the rejuvenated city.