Spanish steps: Spectacularly cut into the hillside surrounding Toledo, this external stair elegantly and efficiently transports tourists up to the historic city centre.

Poised precipitously on a hill overlooking a sharp bend in the River Tagus, the city of Toledo has remained miraculously unchanged since the end of the Middle Ages, when it formed the epicentre of Spanish political, cultural and religious life. Confined within its massive city walls is a dense medieval labyrinth of streets, which now heaves with tourists and their cars. At times it is an uneasy coexistence, epitomizing the familiar dilemma faced by historic centres in how best to accommodate the demands of modern visitors.

The city authorities decided to limit non-local traffic by constructing a new garage for 400 cars at the bottom of the hill. But tourists somehow still had to negotiate the steep topography to reach the historic centre over 100ft (36m) above. An external escalator carved into the hillside efficiently resolves the problem of access and provides a wonderful scenic promenade as a foretaste to the delights of the city. The escalator is connected to the car park by a passageway carefully inserted below the foundations of the existing medieval city walls. This marks the beginning of the route and forms a new city portal.

Constructed in six sections that zigzag up the cliff face, the escalator is supported by a concrete structure and foundations lying on bedrock some 30m below ground. The concrete is coloured a warm ochre that recalls the traditional earthy hues of Toledo's buildings. The inside of the escalator is flanked by a retaining wall which is cantilevered at the top to shelter users, so that the structure appears half buried in the landscape. The division into sections encourages a leisurely upward progress, animated by changing views of the Tagus plain stretched out below. At the top, a contemporary version of a belvedere frames a final breathtaking vista before visitors immerse themselves in the dense fabric and delights of the historic centre.

Great care has been taken to minimize the visual and ecological impact of such a potentially intrusive new structure. From a distance, the escalator is tantalizingly imperceptible, appearing as a series of taut incisions in the terrain. At Toledo, the weight and presence of history and the demands of modern tourism are, for once, boldly and intelligently reconciled.