London’s first ecological tall building and an instantly recognisable addition to the city’s skyline, 30 St Mary Axe is rooted in a radical approach - technically, architecturally, socially and spatially. Commissioned by Swiss Re, one of the world’s leading reinsurance companies, it rises forty-one storeys and provides 76,400 square metres of accommodation, including offices and a shopping arcade accessed from a newly created public plaza. At the very top of the building – London’s highest occupied floor - is a club room that offers a spectacular 360-degree panorama across the capital. Generated by a radial plan, with a circular perimeter, the building widens in profile as it rises and tapers towards its apex. This distinctive form responds to the constraints of the site: the building appears more slender than a rectangular block of equivalent size; reflections are reduced and transparency is improved; and the slimming of its profile towards the base maximises the public realm at ground level. Environmentally, its profile reduces the amount of wind deflected to the ground compared with a rectilinear tower of similar size, helping to maintain pedestrian comfort at street level, and creates external pressure differentials that are exploited to drive a unique system of natural ventilation. Conceptually the tower develops ideas explored in the Commerzbank and before that in the Climatroffice, a theoretical project with Buckminster Fuller that suggested a new rapport between nature and the workplace, its energy-conscious enclosure resolving walls and roof into a continuous triangulated skin. Here, the tower’s diagonally braced structural envelope allows column-free floor space and a fully glazed facade, which opens up the building to light and views. Atria between the radiating fingers of each floor link together vertically to form a series of informal break-out spaces that spiral up the building. These spaces are a natural social focus – places for refreshment points and meeting areas - and function as the building’s ‘lungs’, distributing fresh air drawn in through opening panels in the façade. This system reduces the tower’s reliance on air conditioning and together with other sustainable measures, means that the building is expected to use up to half the energy consumed by air-conditioned office towers.