Ruhr revival.

In the old industrial town of Essen in Germany, a new use has been found for part of a defunct mining complex, in the process restoring a magnificent legacy of the past and providing inspiration for the future.

Essen is the old industrial heart of the Ruhr valley and centre of the den se conurbation stretching back eastwards from the confluence of the Ruhr and Rhine rivers. Long associated with coal-mining and Krupp's armament factories, Essen was the target of Allied raids during the Second World War and was largely rebuilt after it.

The decline of heavy industry in the area since the war has left a hefty legacy of redundant buildings, to which local and governmental pride in an industrial past has turned its attention. The efforts by the Bauhutte, an organisation that finds new uses for old buildings, suggest that destroying such a heritage - by, for example, eviscerating magnificent monuments like Battersea Power Station-will be as great a crime as pulling down the Euston Arch.

Of all industrial monuments in the Ruhr, the most spectacular is the Zollverein XII coalmine which closed down in 1986 leaving an extraordinary landscape drawn from Metropolis, in which vast brooding edifices of plum-coloured brick here and there surmounted by winding gear, rise above newly grown forest. From above, you can see that the forest is intersected by lines of rust-red pipes running from one structure to another.

The conversion by Foster and Partners of the boiler house into a new home for the German Design Centre links the industrial might of the past with the vigour of the present; and belongs to a canon of works by Fosters which have as a large part of their raison d'etrethe dialogue between old and new. In the design of the Sacklet Galleries at the Royal Academy (AR December 1991), and more recently the Duisberg Masterplan, the practice has demonstrated an ability to grasp the essence of what exists and extrapolate from it.

Fritz Schupp and Martin Kremmer designed the complex between 1927-1932. Little is known of the practice, except that there were Berlin connections and, on the evidence, some influences from the more Rationalist elements of the Amsterdam School. Like the rest of the buildings on the site, the boiler house flanked by two wings is steel framed with in-fills of brick and industrial glazing, the thin orthogonal frames of which are traced across the dark brickwork. Echoes of Dudok's Hilversum buildings are present in the single vertical element, once emphasised by a tall chimney, of the facade's composition. The chimney had become unstable and was demolished before Fosters arrived on site. Most of the architects' budget was spent on rebuilding the facade, generally making the structure safe and removing some unsympathetic late additions.

The Centre, which is held in great esteem by German industry, holds permanent and temporary exhibitions of industrial design. The brief called for provision of offices and conference facilities and the creation of exhibition spaces with in the restored shell. Two floors of offices with stupendous views over the site have been inserted into the roof space. A meeting room apparently suspended in space has been built at a lower level, its outer glass wall giving vertiginous views (and causing the one complaint from the Centre's staff - that it transmits noise).

The fine elegance of the exterior scarcely prepares you for the rugged drama of the main part of the interior, the central hall. Much of the listed structure has been left exposed and, at Fosters' insistence, unrestored, so that on entering it you are confronted by exposed brick walls rising the height of a cathedral nave and enormous columns and beams, furnaces, bits of conveyors, miles of copper tubes, and huge nameless chunks of rust-red steel. The interiors of four of the five massive brick boilers have been smoothed over and made to contain two levels of open galleries; while the fifth has been preserved as an exhibition of '30s technology. These galleries are linked by suspended walkways with transparent glass balustrades. At the upper levels where you are suspended high above the ground, you feel as though you are walking on air; and because of the great depth of the building and the density and heaviness of the structures inside it, you are continually moving from darkness to light and back again as you walk between the centre and the illuminated perimeter. It is easy to imagine you are taking part in some symbolic enactment of the march of civilisation.

If by impinging upon the building in this most minimal way, Fosters have enhanced the drama of scale and texture, the Centre's exhibition organisers have responded to the spaces in a somewhat surreal manner. Larger pieces of industrial design like car bodies or wheelchairs are apt to be suspended in mid-air or strewn about the floor; elsewhere are perched a coloured washing-up bowl, a kitchen tap, high upon a massive piece of rusty machinery like the flotsam of an industrial tide.

There are lessons to be learnt from this exercise in re-use. They are Contained in the communal pride in an industrial past and governmental will to preserve its magnificent legacies; they are also contained in the delicacy of the architects' approach. The result is a vigorous centre of industrial design, which is a tribute to achievement and an inspiration to German industry. This is what should have happened to London's Battersea Power Station.