Tunnel vision: a landscaped path from the city of Prague to the castle takes visitors along the verdant deer moat and through a new tunnel under the Powder Bridge. (Design Review).

The tunnel, by AP Atelier, connects the lower and upper parts of the deer moat at the foot of Prague Castle. This park is considered a national treasure and the tunnel is part of a larger plan, originally proposed by Vaclav Havel, to encourage pedestrians to use it better and to create an alternative route from town to castle. The more usual way is to cross the Powder Bridge slung across the valley.

By following the new path, you climb the stony incline of Chotkova Street to the lower deer moat; and walking gently uphill, you trace the bed of the Brusnice stream which runs against you down the valley. By degrees, the walk takes you to the upper deer moat and Pheasantry, and to the castle's north gate. The tunnel occurs where the stream is channelled underneath the Powder Bridge, along the path of a drain buried beneath its supporting mound. In this mound is also interred an older Renaissance bridge, a column of which has been discovered and preserved.

Measuring 84m in length, the tunnel is a long narrow oval, the encompassing arch patterned and textured by the structural brickwork. It is striped along its length by luminance from fittings sunk into the concrete floor. The tunnel is contained at each end by portals inclined in Egyptian manner; and these mouths are framed by concrete embankments that spread out wide to encompass the deer moat paths and open bed of the stream. Entrance from the open air to the dim shadowy tunnel is dramatic and mirrors childhood dreams.

The sequence of materials and textures is an important part of the tunnel experience. These range from stained and patterned concrete of various kinds to stone and brick Externally, there is the cast concrete (coloured by iron filings) of embankment walls and the stone paving and stream bed. Internally, a transition from stained concrete and rough stone to the brick vaulting is denoted by beton brut panels; underfoot, you tread on a surface composed half of fluted concrete, and half of metal grilles which cover the waters of the stream. About halfway along the tunnel, a niche reveals a section of the supporting structure, part of the original Powder Bridge, which has been rescued and restored. Lined with finely levelled cement, the niche is floored with river pebbles.

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AP Atelier/Josef Pleskot, Prague

Project architects

Josef Pleskot, Isabela Grosseova, Jana Kantorova, Zdenek Rudolf Jitka Svobodova, Jlrl Trcka

Photographs

Jan Maly

1 Entrance from lower deer moat to tunnel beneath Powder Bridge.

2 Oval tunnel lined with brick. Underfoot are concrete and metal grilles over Brusnice stream.