Singular suspension.

Gracefully spanning Bilbao's Nervion, this pedestrain bridge by Santiago Calatrava explores the expressive civic potential of Urban infrastructure.

Designed by Santiago Calatrava, this new pedestrian bridge in Bilbao forms part of an enterprising plan to reinvigorate the Basque city through a series of urban design initiatives and bold individual proyectos. Described in detail in last month's AR, the proposals include infrastructural improvements and finding new uses for the derelict swathes of land left by defunct maritime industries along the banks of the River Nervion. Calatrava's spectacular arched span lies just upstream from the new Guggenheim Museum and links the disused Uribitarte warehouse complex with the Campo de Volantin, a sweeping riverside promenade on the opposite north bank. As well as providing a new crossing and meeting point, the bridge is part of a larger scheme to redevelop the Uribitarte warehouses into offices and flats.

Historically, Bilbao's topography and engineering capabilities have contrived to produce some curious structural experiments, such as the nineteenth-century Puente de Vizcaya (designed by a disciple of Eiffel), in which vehicles and people are ferried on a moving platform slung from a set of cables; and the Ascensor de Begona, a free-standing lift tower designed to carry people up from the old medieval core to the hills above. With its dramatic curving profile effortlessly traversing the Nervion, Calatrava's contemporary addition extends this lineage of industrial ingenuity.

The elegantly minimal composition is based on the two opposing curves of the bridge deck and its supporting arch. Pitched downstream at an angle of 80 degrees, the 14.6m high steel arch appears on the point of leaning too far, like a frozen pendulum unable to return to its natural point of equilibrium. Strung from the arch, a delicate filigree of cables supports the 71 m long span of the bridge deck. Accentuating the ephemeral quality of the structure, the deck is made from panels of translucent glass, supported by narrow stainless steel ribs, like the spiny backbone of a fish. Lateral support is provided by a pair of sinuously sculptural precast concrete platforms moored to each bank.

For Calatrava, bridges are not merely utilitarian objects in the landscape, they also have a civic and social dimension. With the recent Trinity Bridge in Salford for example (AR March 1996), two distinct areas of the city were joined together, bridging the physical and social divide between the local populace. Here, the new bridge represents the renewal of a city. At night, its symbolic purpose is emphasised when both the gleaming white structure and the translucent deck of the bridge are illuminated, reflecting a dramatic play of light on to the river surface. By treating his bridge commissions as public places, civic icons and opportunities for structural invention, Calatrava challenges the tenets of contemporary bridge design and encourages a re-examination of the visual and social potential of urban infrastructure.

Architect and engineer Santiago Calavatra

Photographs Paolo Rosselli