Steven Holl loves China. Linked Hybrid is the first of four huge China projects designed by his practice to be completed. On many counts, it is Holl’s favourite: for its mammoth proportions but especially for the opportunity to provide Beijing with a residential complex on a par with New York’s urban dimension with pedestrian areas and public services. Two of Holl’s other three other projects - the Nanjing Museum of Art & Architecture and the Vanke Center in Shenzhen - will be completed during 2009 while the third, the Sliced Porosity Block in Chengdu, will be finished in 2010. Holl is proud of the opportunity to provide Beijing - after the Olympic Games now famous for its iconic buildings by celebrity architects - with a complex that aims to enhance liveability in a city whose development has largely disregarded even the most elementary requirements of ordinary citizens. Like many other large residential complexes around the city, Holl was originally asked to build “point towers isolated at the base; gated communities with no services”. He insisted, however, that what was needed was “a project that has a vision for urban interaction, one that has services, and is open to the public”. The upshot was a complete change of heart by the developer. As a result, the 750 apartments are now flanked by commercial areas, a public garden, hotel, nursery school, Montessori school, underground car park and, as a central aggregating feature, a cinemateque. The key spatial-organisation choice was to create two public-area levels or loops. The more traditional ground level has shops, the cinema and a large reflecting pool. On the upper level, spectacular pedestrian walkways link the eight towers between the 12th and 18th floors, providing sweeping views over the city. This “sky-loop” is accessible to the public and creates a “kinematic” thoroughfare through the whole complex in an upward movement going from one public function to another: from the swimming pool on to the gym, auditorium and gallery up to the top-storey hotel. The constantly changing views offered by these overhead walkways is a signature feature of this American architect who since the nineties has been particularly concerned with the dynamic perception of spaces, in stark contrast to architecture conceived to be seen from one static viewpoint. The pedestrian bridges themselves are structurally sophisticated, lightweight and mounted on flexible elements that will oscillate and absorb the shocks of eventual earthquakes. Flexibility is also the distinctive characteristic of the interior spaces. Moveable partition walls in the apartments make changes to layout a simple matter. The modular aluminium cladding on the building façades are reminiscent of another Holl project, Simmons Hall in Cambridge, Massachusetts, completed in 2002. In the Beijing complex too, window and door recesses and lower building sections are coloured. But unlike the Massachusetts project, the colour pattern here is not graduated but random: I-Ching divination coins were thrown to establish the sequence of colours, which hark back to traditional Chinese architectures. Linked Hybrid is an innovative project in terms of environmental sustainability, not so much in terms of the technologies applied but because it is one of the first projects on this scale to use geo-thermal wells. A network of 660 wells sunk 100 metres deep under the foundations supplies the underfloor heating and ceiling air conditioning systems, ensuring temperature stability, whatever the season. Greywater is recycled and all roofs have been turned into gardens for residents. The north side of the site, used as a tip for the earth removed for the underground car park, has been landscaped into a public garden. A series of artificial hills separates sports fields, teahouses and an area for meditation. With this project, Steven Holl Architects makes their statement in the on-going debate regarding development models for oriental cities. Linked Hybrid has been called an “open city within a city” to emphasise how project scale and programme variety are fundamental to urban quality. It begs the question though not so much whether this complex - a commercial mall set among high-rise residential towers - is a real remake of the New York urban model but whether it is truly a step toward a sustainable urban model. In any event, it is an important contribution to the debate on how public space should be put to use in the Chinese capital.