Light cone.

An extension of a tile coating headquarters in northern Portugal is a landmark on a busy main road and evocation of one of the country's oldest industries.

Revigres, the headquarters of the Industria de Revestimiento de Gres (clay tile coating) is at Agueda, a town north of Coimbra in northern Portugal. Alvaro Siza's extension to the existing administrative building provides a showroom, library and archive room, and big staff dining room.

The building has been designed as a landmark, lying, as does the existing administrative building, along and west of the main north-south national highway. Linked to the existing building by an elevated gallery, the extension has a main axis running parallel to the motorway. From the road, as you flash by in a car, the building registers an intriguing - even exotic - presence above a long horizontal green bank. Set on a granite plinth and surmounted by a gleaming white, truncated cone, it appears to be a complex composition of white volumes stepped up towards the southeast corner and back from the road. If the stacking and layering of simple imperforate forms recall the traditional architecture of more southerly latitudes, the conical chimney is reminiscent of the tapering flues of pottery [furnaces.sup.1]. Here the cone has been transformed into a lightwell illuminating the exhibition hall, which is the heart of the scheme.

In other ways the building is not as it seems from a glance in passing. Rather than a complex composition of many parts, a closer inspection reveals it consists simply of two interlocking bodies which together describe a kind of L around an open forecourt.

The main one, containing the exhibition hall, forms a square block to the south, and, built upon a sloping site, it is partly raised on columns to provide a covered entrance under which visitors arrive on the south-east. Running along the west side of the site is the secondary long arm of the L, its curving roof softening linearity. On the ground floor is the large dining room and kitchen. An archive room is the interlock between the two bodies. Above, on the first floor, there are offices and meeting rooms giving onto a long terrace, and passage to the gallery link with the main building.

The initial impression of complexity derives from the stacked roof of the exhibition hall, the tiers ascending and descending and, inset with clerestory windows, spun around the big cone.

Given the traffic blown circumstances, Siza has elaborated the vertical and created an extraordinary interior space. His spatial sequences, the suggestion of volumes hollowed out of the solid and manipulations of light and shadow often suggest the influence of Islamic architecture. And nowhere more so than here.

As usual in Siza's buildings you have the sense of moving through layers, through spaces that vary in size and intensity so that you continually experience differences in scale and light. From the entrance, you pass into a double-height lobby, floored and panelled in pale marble. From this enclosed space you have a glimpse of the sculpturally expressive heights of the hail above. To the right a flight of marble steps expands in width from bottom to top and delivers underneath the edge of the cone. Above and around you, space is modelled by the underside of the receding roof and cone; and by luminance from the skylight and clerestoreys. Tempted to look into the cone's core, you experience the limitless void of an Anish Kapoor sculpture.

1 Among the most potent examples are those added to the monastery of La Cartuja, Seville, when it was converted into a pottery during the lane nineteenth century (AR June 1992, pp55 and 58).

Architect

Alvaro Siza

Photographs

Ducclo Malagamba

1. South-east corner of the building from the motorway.

2. Entrance under cover on south-east.

3. Stairs from entrance lobby up to showroom.

4. Showroom and sample racks.

5.South-west corner of showroom with reception.

6.Interior of cone.