Karakida Community Center by Chiaki Arai in Tokyo

For Chiaki Arai Urban & Architecture Design, respecting the history of a site is of paramount importance with every project. In the case of the Tokyo-based studio's latest work - Karakida Community Center in Tama, Tokyo - an undulating grass roof acts like a palimpsest of its former incarnation. 'The site was a small hill,' explains Chiaki Arai. 'The memories of the people who played on it are encapsulated by the building.'

Built on a sloping site, the western end of the structure - which accommodates a community hall and library - is on two floors. The eastern part, which houses a children's centre, is single storey.

With its delicately patterned concrete walls, the exterior of the building has a welcoming, almost anthropomorphic look (this is, after all, a building for children). Interiors, meanwhile, are kept simple and spacious thanks to tubular steel columns and an elegant combination of glass, wood and the same patterned concrete.

In 2009, we featured Arai's Ofunato Civic Cultural Center and Library, with its sweeping layers of terraced concrete, in our 'Fab 40', and this new building displays the same virtuoso control of the medium, which he imbues with an unexpected warmth. The award-winning 63-year-old architect, who worked for the Greater London Council in the 1970s before setting up his practice in Tokyo in 1980, was little known until he turned 50 - and actually considered giving up the profession a decade ago. With this latest work, you can't help feeling he's only just getting into his stride.