Transformation in Madrid.

The Villahermosa Palace in Madrid houses the larger part of the Thyssen-Bornemisza collection of paintings. From 1948 the collection had been open to the public at the Villa Favorita near Lugano in Switzerland; but after prolonged negotiations, the owner (whose wife is Spanish) agreed to lend the paintings to Spain f or 1 0 years. The fact that the Villahermosa was available and empty played a significant part in the decision.

This private collection, containing a number of outstanding paintings, is astonishing in its scope. Displayed in a setting designed by Rafael Moneo, it consists of about 800 paintings arranged in chronological progression that, beginning on the top second floor, moves from fine examples of Italian Primitives and the Quattrocento, through the Flemish and Dutch and later European Schools, and via America to the twentieth century

In Moneo's abstract and luminous interior, the paintings have acquired a particular jewel-like quality. (Only the enormous chocolate box portraits of the von Thyssens on the ground floor strike a jarring note.) The Villahermosa stands, as does the Prado, off the Paseo del Prado; a broad boulevard laid out and planted in the eighteenth century during the reign of Carlos III. Its southern elevation, the site of the original main entrance, is bounded by Carrera de San Jeronimo, once the most fashionable promenade in Madrid. The present Neo-Classical exterior dating from the beginning of the nineteenth century was the work of Antonio Lopez Aguado who, in shifting the original entrance from the livelier southern side, made the quieter north facade with its garden the principal one. Paradoxically, his plan for the interior with a grand central staircase suggested entrance from the grand boulevard. The most drastic internal changes took place during the 1970s when the building was gutted to make way for modern banking premises and the main entrance was again moved back to the south.

Moneo's achievement is to have taken hold of a discordant body and out of it to have created an interior of abstract harmony His is an exceedingly civilised and civilising building. Its ordering, while fulfilling the functions of a modern museum, relates to Aguado's exterior and the main north to south axes of the urban context, while acknowledging earlier palatial origins. Having decided to restore the integrity of the handsome Neo-Classical shell, Moneo moved the entrance back to the secluded north side and restored the primacy of the north facade. Visitors to the museum approach it, as in Aguado's time, from the tranquil garden.

Inside, Moneo has returned, as he has in the past, to Roman/Moorish archetypes - this time of the grand dwelling. The plan of the building, based on the existing structure, revolves around a long grand open hall. Illuminated from above, it rises from the ground to encompass the first floor level and establishes a logical longitudinal axis. The purpose of the plan and form of the hall, though not its dimensions, is repeated in the hall for temporary exhibitions in the basement, and in an open patio on the second floor. Apart from the basement, which otherwise contains various services, each floor is divided into small galleries generally running at right angles to the external walls and connected by ambulatories.

Some of the galleries are enclosed by walls, some by screens; but the rhythms set up by the series of spaces so created relate to those of the exterior. The casual visitor is likely to sense such harmonies, rather than perceive them in an overt way, being distracted immediately by the ravishing impression of terracotta-pink plaster and pale stone which are the principal internal materials (and naturally enough by the paintings). By deploying pure planes of varying light and colour, by the richness and simplicity of the materials, Moneo has created spaces that convey both the elemental and the opulent.

Standing at the entrance, the visitor's eye is drawn past simple stone monoliths that form the elegant barrier, down the length of the glowing luminous hall and up to a first floor gallery cut into the monumental plane of the western wall. Seen from above, the simple volume has an abstract Moorish quality, articulated by the kind of rosy light and shadow reminiscent of southern latitudes. Elsewhere, scale is dramatic; monumental walls breached by simple openings have been constructed to hide concrete supports inherited from the last remodelling of the interior. A staircase to the east of the entrance is a thin luminous slot through the building.

In his review of Moneo's Merida Museum, (AR November 1985), Peter Buchanan noted that underlying the architect's work is a Rationalist sympathy inspired from Italy, but deployed less dogmatically. Moneo has, Buchanan continues, 'a faith in the virtues of a typological approach to design, and a concern for civic memory and history. And typical of Spanish architects, but unlike Italian Rationalists, his work reflects a fastidious concern for materials and construction'. On the evidence of Villahermosa, such observations hold true. 1 0 years on. The flat stone detailing round the plastered walls is a constant delight, as are the long opulent expanses of stone floors, the pale creamy stone in places being laid geometrically with dark red stone. As in the Merida, there has been no attempt to play down architectural presence to avoid competing with the paintings. Illumination is by both natural light and the sophisticated artificial lighting systems now obligatory in modern museums with delicate exhibits. This is above all a modern building, with space and function determined by a sensibility and intelligence attuned not just to modern needs but to something more eternal.