Grand gesture.

France's new Bibliotheque Nationale is a singular convergence of architectural and political ambition. Here we examine how the monumental complex relates to the city - a subsequent appraisal will consider how well the building serves its various users.

Both conceptually and physically, the new Bibliotheque Nationale is le plus grand of all the vaultingly ambitious Parisian Grands Projets. A major political and cultural constituent of Francois Mitterrand's second term of office, it was symbolically launched on Bastille Day 1988 when the French president announced his intention to create a 'very large library of an entirely new type'. Although Dominique Perrault's monumental complex appears to reflect Mitterrand's Boullee-esque preferences (the cube at La Defense and the twin pyramids of Pei's Louvre being the most literal examples), the effectiveness of its realisation is singular, particularly when compared with the procrastinatory muddle enmeshing the British Library. Unlike his British counterparts, however, Perrault has benefited from confident and enlightened patronage - political support for the huge enterprise has been unflinching, despite animated public debate - and this has undoubtedly served to expedite the scheme's progress from visionary competition winner to impressively consolidated civic and cultural landmark.

Soon after Mitterrand's announcement, a site for the new building was swiftly procured from the city of Paris. Originally the location for an aborted Expo to mark the bicentenary of the French Revolution, it lies on the edge of the Seine, in the unfashionable 13th arrondissement. This dreary south-eastern corner of the city, dominated by the crude, vertical extrusions of the Place d'Italie, forms part of a rejuvenatory 'Seine-Rive-Gauche' masterplan. The aim is to mirror the scale and scope of the redevelopment of Bercy on the opposite bank, now colonised by Chemetov & Huidobro's gargantuan Finance Ministry (AR August 1989), Gehry's riotous American Centre (AR August 1994) and Jean-Pierre Buffi's sensitive attempts at urban recomposition (AR June 1995). More specifically, development of these languishing arrondissements extends the eastern boundary of Paris both physically and psychologically. Eventually the new library may be connected to Parc Bercy by a pedestrian footbridge across the Seine, creating new routes and animating corners of the city.

Being the focus of such a hectic transformation has made a series of more complex demands on the building, beyond merely accommodating some 12 million printed books, 300 000 collections of periodicals, plus generations of scholars, researchers and ordinary book lovers. In a description as taut as the minimalist abstraction of his architecture, Perrault defines the resolution of these demands as 'Une place pour Paris, une bibliotheque pour France' emphasising the symbiosis between the city and its monuments. Here, between the louche peaks of Place d'Italie and the rumbling maw of Gare d'Austerlitz is a nouveau monument, of heroic (even pharaonic) proportions, and glacial, Euclidean perfection.

The building's haiku-like, 'complex simplicity' is derived from Perrault's ruthless distillation of a colossal brief into a deceptively disarming (and curiously wilful) organisational proposition - readers below, books above. This is achieved by placing four towers at the corners of an immense rectangular block, which is gouged out to form an inner courtyard. The top of the rectangular block is in fact a vast, elevated podium, of roughly the same dimensions as the Place de la Concorde, but of an entirely converse character. The podium is accessible from the Quai Francois Mauriac by an imposing tier of dark timber-clad steps that run the length of the building, defining and confronting the street edge.

From this angle, the prospect is frankly Orwellian - a quartet of seamless, sinister towers lowering over the daunting steps. However, this monolithic staircase must be ascended to locate the escalators at each end of the podium. These transport visitors down into the inner realms of the mastaba beginning with two floors of public reading rooms and increasing in scholarly sanctity the deeper you go. The lowest floor, reserved for the high priesthood of researchers, contains a monastic ambulatory around the perimeter of the secret inner courtyard. Here it is possible to contemplate the cloistered stillness and the mirage-like serenity of nature (albeit imported) in the form of over 200 transplanted oaks, hornbeams, birches and pines.

Above the artificial datum of the podium is the sentinel quartet of towers. Each 20-storey edifice contains seven floors of offices, 11 floors of storage and two levels of plant. The L-shaped plans vaguely allude to open books, but the original cumbersome allusion has been diluted and refined by the weightless luminosity of the final built forms. Behind the immaculate glazed skin is a shifting mosaic of okoume veneered panels. These movable sunscreens (fixed permanently shut in book storage floors) are intended to protect the tower's occupants, both animate and inanimate.

Yet as the four transparent silos housing the creme of France's 500 year old printed book collection hover ethereally over the mongrel blare and dirt of the 13th arrondissement, it remains to be seen whether they have the gravity to aggregate the city around them or remain monumentally dislocated follies of political ambition. At present it is too early to judge - Perrault's impulsive geste architectural will only find its real meaning and identity once the surrounding morass of the Tolbiac neighbourhood has been slowly coaxed and coalesced into some kind of permanent form. Moreover, the building still waits to be enlivened by the habits, routines and idiosyncrasies of its multitudinous users. This crucial colonisation is still some time away and will be the subject of a subsequent AR appraisal. For now, the Bibliotheque has the appearance of a sealed, enigmatic, mute monument, but it is worth recalling a remark made by Mitterrand's historical favourite, Boullee, in a preface to his recommendation of 1784 that a new library should be built in Paris - 'A nation's most precious monument is beyond any doubt, that which is the repository of all the knowledge that it has acquired'.