Municipal assurance.

Juan Navarro Baldeweg's refined local government complex in Merida shows how a large building can be sensitively inserted into a historical city fabric.

Extremadura is the huge region of heathland and forest south-west of Madrid extending west to the border of Portugal and south to the Sierra Morena. The capital of Extremadura is Merida on the Guadiana River. It was once the capital of the Roman province of Lusitania and contains more important remains than any other town in Spain. To the Roman bridge of 64 granite arches that spans the river has been added a bridge by Santiago Calatrava, the curves of which structure echo those of distant hills. The horizontal nature of the rolling landscape and the subtle setting of the town within it makes Merida particularly vulnerable to insensitive development; for it must be immediately visible, destroying the delicate harmony between the natural and the man-made.

Juan Navarro Baldeweg's regional government offices are set on a sloping site on the river bank, extending out along the line of the old city wall. The site is a crucial piece of the fabric of the town. It links the Alcazaba - a Moorish citadel of Roman origin and the Roman bridge in front of it, with an important crossroad leading to Calatrava's bridge in one direction and into the town in the other.

Since the building would form an integral part of the city skyline, particularly when seen from the opposite bank of the river, the architects had to grapple with a number of conflicting problems. The size of the scheme was large; for as well as containing the Governor's and Deputy Governor's offices, the building had to provide offices for the four departments that make up the regional government of Extremadura. At the same time, it had to respond to the sweeping countryside and slow breadth of the river while respecting the scale, mass and antiquity of the city. The building - really a complex of different departments - had also to straddle an extensive and precious archaeological site.

Navarro Baldeweg's contextual sensibilities have been frequently remarked (see ARs May 1986, January 1990, July 1990). He trained as a painter and has, it is said, a painter's regard when placing buildings. Certainly here in Merida he has managed a difficult task cleverly, dissolving the bulk of the scheme by stretching it out horizontally, stepping it down and across the uneven site while maintaining a constant roofline, and cutting into the mass to reveal an apparently transparent core. Where the scheme approaches Calatrava's bridge and traffic, he has chopped the end off to form a separate building linked by a handsomely detailed courtyard and presenting a diaphanous public front. It is set back from the main line of the building so as not to overshadow entrance to the bridge and to leave room, visually speaking, for the swirl of a roundabout. With all of this, Navarro Baldeweg has created a restrained, dignified presence.

In contemplating the scheme from the other side of the river, some resonances become plain. The rhythms and scale of the ruined citadel are echoed in the facade of the new building; the indentations and constant roofline stir memory of a city wall and ancient fortifications. More prosaically, the recessed bays visually and physically depict the separate government departments, the transparent walls lining their interiors admitting daylight to the various offices. The orientation of the bays is west, and interiors are shielded from late sun by metal sunshades.

The way the structure meets the ground over Roman remains, unearthed when construction began, has been treated with care. The building floats above the excavations, with the minimum of structural supports. Bridges span newly created 'archaeological heritage sites', platforms project over the works for the purposes of contemplation, and flights of steps finely detailed with glass balustrading lead up to entrances at first floor level. Lightwells at the rear of the building trace the path of a Roman road and shed light over the ruins.

Materials are handsome and intended to relate to those of the town massed up behind. The building is faced with grey granite and white stone. Those parts of the lower section in contact with the ruins are of rosy/ochre brickwork, reminiscent of the Roman.

Navarro Baldeweg was not responsible for the design of the interior - unfortunately, as it has turned out. For this is a subtle and supple scheme that expresses the intellectual rigour of the architect. The forms and materials that make up the ensemble anchor it in time and space - it is inescapably a modern work of architecture that at the same time respects its context - yet floating as it literally does above evidences of more ancient civilisations, it has considerable metaphorical force.