Plastic arts.

The landlocked Dutch province of Limburg is home to both Dom Hans van der Laan's work at the Benedictine abbey of Lemiers and Wiel Arets' strikingly new Academy of the Arts in Maastricht. In a world of eclecticism and regurgitating images, both projects offer a sense of determined calm; in the earlier case - the monastery - of a gentle being in its world, in that of Arets a dialectical attitude towards current disorder.

To attempt to compare a rural and contemplative sanctuary of monks to the inherent multiplicity of an urban, contemporary art school may initially appear arcane. Van der Laan's courtyards and halls - with their concrete floors, earth-rubbed brick walls, and skeletal timber furniture - hark back across time to some stable origin of things. Arets' Academy building - with its cranked geometries wrapped, or made, of translucent blocks - is unmistakably of the more problematic present. Yet, as well as a curious currentness, Arets' building exudes an essentiality not unlike the compositional truthfulness of van der Laan. This essentiality, distilled through use of materials and light, evokes a pervading sense of mystery about the realised building.

The Maastricht Academy embraces fashion, graphics, industrial design and experimental fine arts in a medley of buildings dating from the eighteenth century to, until the intervention of Arets, the 1960s. His site is two lots on the western perimeter of Maastricht, in an interstitial zone where the cloistered and cobbled precincts of the ancient, ecclesiastical city give way to the functional arrangements - housing, education, light industry - of the recent past. The new building brings together the disparate constituents of the Academy and is part of a new residential square - the Herdenskingsplein - planned by the Delft firm of Mecanoo. Arets' architecture has therefore a double potential. Functionally, it must accommodate the various and necessarily messy departments of the Academy. Urbanistically, it not only presents itself within the texture of the city but harnesses its position to mark the inevitable growth of that fabric.

If you approach from the Old Town, you might not even see the building. This quality of invisibility - of stealth, considering its chunkiness of form - is attributable to the gleaming surfaces of glass block and a pair of spreading chestnut trees. Arets has joined his sites on either side of Herdenskingsplein with a concrete-sided bridge, a double beam spanning clear and 11m above the public realm. Especially camouflaged in summer, the bridge is the project's central armature and abstract gateway to the square. It allows the Academy to function with a single 'front door' and, in a fully characteristic way, reveals its nature only when viewed from below - or, conceivably, from above. Both its horizontal surfaces are made from panels of glass blocks so that the transverse motion of the building's users becomes a kind of kinetic public X-ray.

The sole, raised entrance to the total complex is through a 1960s horizontally banded facade, with the existing buildings of the Academy on the right. Here the architect's minimal action is to blacken walls and insert new glass doors. Through an internal porter's station, you look into a shared courtyard at a rather prim eighteenth-century edifice beyond. To the right is the first of Arets' two new blocks, a square vertical extrusion. This first intervention contains the communal programme, with a library next to the foyer but 1.3m below, so that there is discrete presence but a volumetric disjunction in registering the presence of the new. Inboard from the library - which repositions the visitor at the level of the Herdenskingsplein - a raw concrete ramp leads both up and down. With light falling towards its edges, this ramp begins the architectural promenade which leads to the other 'L' or triple-cubed mass lying on the other side of the sealed bridge.

Downward, the ramp terminates at an enclosed lecture hall, a stable space with tiered seating and deep concrete roof beams. The cavern-like character of this volume seeps into a triangular void between the top of the hall and a flank of the 1960s building and up beyond sheets of glass into the ramped slot animated by the appearance and disappearance of passing bodies. Both vertical shafts of light result from the geometric discrepancy between the pure co-ordinates of the new intervention and the neighbouring conditions. Upward, the floor of the ramp spreads from its central spine to be held free of surrounding walls - an interstitial steel bar has had to be inserted. The ramp's slope is adjusted to produce a discernible steepness towards the top, towards the percolating light. The uppermost room is the Academy's cafe, a programmatic suggestion of the architects and the ideal venue to receive and reveal the vertical and horizontal systems of ramp and bridge circulation. From across the Herdenskingsplein, the bridge protrudes into the cafe volume at a slightly cranked angle. This shift is due to the perimeter of a previous structure on the farther site but produces, in the physical transition between Arets' volumes, a sense of almost hermetic relocation. This bridge is a simple long room with deliberately empty space caught by the planes of concrete and glass block. The studios beyond occupy L-shaped floor plans divisible by glass screens and are freely strewn with the saws and mannequins and drafting boards of the students - the floors are already paint-splattered. The studios are reached from an open stair leading back down to basement workshops and are partly lit through the glazed stairwell from an excavated cavity, which serves in summer as an exhibition pit. On each stairwell landing are small bathrooms that occupy but do not touch the translucent corners of the building.

The glass blocks spread as a total membrane, creating an identical inner and outer morphology. The panels of block are able to swell at corner, soffit and parapet conditions. They are composed of twin segments, fabricated off-site and generally with a slot at eye-level to provide view and ventilation. This thick veil of a membrane is held away from the concrete frame and has slightly more transparent blocks aligned with the window openings to further dematerialise the mass. Throughout, the architect's palette is rigorously simple. With Wittgensteinian austerity, fittings such as in-situ concrete desks, steel stair handrails, and low, free-standing radiators augment the form-marked concrete and wire-gridded glass. This, with horizontal slots in the bridge giving glimpses of the exterior world and internal glazed doors of deep steel frames, seem to posit Arets' construction as some sort of viewing mechanism.

This first big work of the young Dutch architect supplies functional space and facilities within a necessarily complex envelope. Spatial manipulation and contiguity of surface have achieved the desired unity of expression and it is perhaps that desire for unity within a complicated context which most seriously informs the total design. There is not only the principal form, erupting into and fabricating space, being both active and passive, but every moment is seized to bring both materials and people together.

It is the extraordinary focus on the essential, to the banishment of any possibility of decoration, which reminds one of van der Laan. It is extremely rare to have new construction suggest such accolades as 'ideal' or 'pure' or 'spiritual'. But the monastery and the Academy stimulate, without sentimentality, such a response.