Background Madrid is a fast-growing city, with population growth resulting largely from immigration into the urban area. The city is expanding in particular to the south-east, with the development of the Vallecas area. At the time of project conception, 26,000 new apartment dwellings were being built, ranging from small units to larger, upmarket developments. Unlike the other areas in Vallecas, the UE1 sector focused on by the project was predominately public land and its development was therefore largely in the hands of the local authorities. The 5,793 flats being built here were largely council property, and the resident population were to comprise mainly low-income groups. It was feared that the character of the neighbourhood would be determined by the predominance of mono-functional housing blocks, as the original intention of providing residential areas with local shopping facilities had largely yielded to commercial interests favouring large-scale shopping centres to be located further away. Objectives The project sought to contribute to the environmentally and socially sustainable urbanisation of the UE1 sector. Conventional urban planning for the boulevard that forms UE1’s main axis would have led to a solution typical for many recent residential areas in Madrid’s outskirts: a 550m long and 50m wide stretch of pavement and poor vegetation, symmetrically lined by two-lane traffic and parked cars, bordered by 17m high residential building blocks and exposed to wind, dust and summer temperatures that can peak at 40°C. The beneficiary, Madrid’s municipal housing and land-use authority (EMVS), aimed to counter these adverse conditions, along with the social problems generally associated with the deterioration of public space in all of Europe’s major cities. In late 2002, the unit was granted LIFE co-financing for a project that foresaw the “bio-climatic design and conditioning of an open space” – though without specifying exactly how this was to be achieved. The objective was to evoke the Mediterranean spirit of outdoor public life through a contemporary urban design project for an open space in the newly developed district of Madrid. A design competition was held and won by the studio Ecosistema Urbano, who proposed to line a semi-pedestrianised boulevard with pavilions that would act as “air trees”, providing shade, ventilation and vegetation, whilst functioning as “social activators” - bringing people outdoors – in the yet-to-be-built neighbourhood. Results The project resulted in the design and construction of an eye-catching installation that aims to create a conditioned public area that affords a comfortable outdoor microclimate, promotes social interaction and provides the population of an anonymous new neighbourhood with a sense of identity. The prototype pavilion consists of 17 metre tall steel cylinders (using 80 percent recycled steel), with inner surfaces overgrown with ivy. At the top, funnels draw air into the cylinders. When temperatures reach 27 degrees, ventilators activate and propel the air down into the cylinders and through dampened cellulose panels, creating a cloud of water vapour and reducing the temperature of the falling air by 8 to 12 degrees. The pavilions therefore offer both shade and cool air. Because the design functions best at high temperatures and low humidity, it is ideal for – and transferable to – most Mediterranean cities. The designers expect the temperature under the pavilion to be 10 to 15 degrees cooler than the surrounding area. The benefits of the pavilions are that they are quick to assemble, and reassemble; they are low maintenance; they can be planned to fit in with the urban environment; and other features such as energy-efficient lighting can be incorporated. The prototype pavilion in Madrid also has symbolic value that should not be underestimated. EMVS wanted to establish landmarks as reference points in the newly developed areas, and the air tree pavilion with its futuristic look achieves this – it has been given names locally like “el arbolito” and “the rocket”. EMVS expects the new innovation to help revitalize the public space, improve the local climate, and create a sense of neighbourhood. Furthermore, with photovoltaic panels installed at the top, the pavilions pay their own running costs – and even generate a surplus to cover maintenance costs. Following the development of the prototype pavilion, EMVS is planning to build two more along the same boulevard. One will have a screen for projecting films, and the other will have a playground area. The full benefit of the pavilions will be felt in two years' time, however, when the ivy has grown fully in its interior.