Surface tension: Thomas Heatherwick's characteristically inventive, seductive and radical approach to materials finds vibrant expression in this project for a city square.

Known for his energetically experimental treatment of materials (ARs January 1998, July 1999 and November 1999), Thomas Heatherwick's latest project brings a magic carpet to the centre of Newcastle, enlivening and animating a desolate public realm. In 1996 Heatherwick won an international competition staged by the local council to design the city's first new square for over a century. The long narrow site, next to the Edwardian pile of the Laing Art Gallery, was particularly challenging -- more disused road than square -- surrounded by an undistinguished assortment of buildings. At one end, a utilitarian steel staircase brought people into the space.

As the potential for intervention was limited, Heatherwick's response was to concentrate on the surface of the square. Existing paving materials also seemed limited, so Heatherwick, in collaboration with a team at Sheffield Hallam University, undertook to develop an entirely new substance. Heatherwick wanted a strong, sensuous colour to unite and invigorate the urban space. The outcome is a swathe of gleaming blue a spilt pot of paint. Made of crushed blue glass from discarded sherry bottles set in a white resin, the tiles were developed following exhaustive research into safety, aesthetics and durability. Now in full commercial production, the resin-glass composite is extremely hard wearing and can incorporate different types of waste glass to achieve a variety of visual effects.

Tiles are laid in long lines picked out by inlaid strips of brass. The cerulean surface appears almost animate, pulling back around trees and leaning up against the gallery walls. In places it is punctured by bollards and peeled back to form benches, revealing glazed voids packed with multi-coloured fluorescent tubes that scintillate seductively with kaleidoscopic light. The perimeter of the blueness is edged with trees (an oak, two chestnuts and four London planes), all mature specimens with the necessary robustness to survive the exuberant ravages of pedestrian throngs. Benches are polished precast concrete with armatures of hand-crafted brass.

A new helical staircase delivers people into the square at its eastern end. Made of laminated timber by local Tyneside boat builders, the spiral form resembles an outsize snail's shell or giant woodshaving. Elsewhere, the space is treated with deliberate municipal rigour and plainness. Regulation paving surrounds the azure carpet emphasizing its exotic other-worldliness. Bollards and light fittings are catalogue standard. Nothing distracts from the swell and shimmer of the sleek blue surface that slinks enticingly through the gloom and dourness of the city.