Dramatic art.

The Mexican National School of Theatre creates a gigantic stage on which the volumes of the building become actors in a mysterious drama.

The Mexican National School of Theatre is nothing if not dramatic. It stands on an awkward triangular site at the extreme north-western tip of the campus of Mexico City's National Centre of the Arts at the junction of a couple of roads. From these, its great bulging vault can be seen for quite a distance and the new school acts as a landmark for the whole complex.

Closer acquaintance reveals that what appeared at first to be some vaguely industrial building is far from being simply utilitarian. The huge silvered corrugated steel vault is seen to be open at both ends and to contain a collection of strange and diverse forms and spaces.

The vault is created by bending white painted 24in (610 mm) tubes to curve over the main span. The tubes have pin-jointed bearings at each end; they are held to their curves and stiffened by trussing systems of steel cables.

So the huge structure seems extraordinarily light and the space it contains is made ethereal, a reticent and elegant background for the events it contains. The effect is enhanced by creating a clerestory at the apex by making the curve of the cladding on the northern side of the vault rather steeper than that of the structure, so hot air can be released and sunlight can be brought in at high level to be reflected off the silver skin, making the space luminous.

Its great height is explained by the fact that it has been made tall enough to accommodate the fly-tower of the main theatre. The auditorium of the theatre is expressed into the vaulted space as a travertine clad box which is approached by the public from a mezzanine which is connected to the ground by a double ramp and under a canopy in the side of the curved vault. The mezzanine is made like a gigantic table which whizzes west into the otherwise empty volume of the vault. It offers much potential for informal dramatic happenings.

Above the auditorium is the library, with its reading area expressed as a tray looking down into the great space. On top of this, a tapering timber-clad volume shoots up two floors containing the video and audio sections of the library, with at the topmost level, the scenographic collection, under a delicate glass roof through which controlled light falls from the vault.

Along the whole south side of the vestibule to the west of the theatre/library nexus is a long thin rectangular block which at ground level contains dressing rooms and the experimental theatre.

Above these is a level for administrative offices, then there are two stories of classrooms for acting. These spaces are served by glazed galleries that look down on to the vaulted space but all of them look out almost directly south.

To prevent them becoming intolerably hot, their glazing is protected by an elegant and delicate brise soleil made of 40 mm square redwood strips. The screens are cantilevered from the aluminium and glass walls of the upper floors and allow people in the rooms to get some notion of the world and climate outside, while giving the public a glimpse of the room structure within, so modulating the scale of what could otherwise have been a faceless facade.

It is a curious thing, this drama school, wasteful you might think in the volume enclosed; excessively gestural, but what opportunities for drama it gives, and what a moment to the art.