The Museum as Cathedral: Modern Art's Latest Shrine

San Francisco's new $60 million Museum of Modern Art is a remarkable and authoritative building that is tough to love and impossible not to admire. Architect Mario Botta's response to the helter- skelter American urban environment is a great clenched fist of a building.

Dominating the eastern flank of a major urban-renewal project, Yerba Buena Center, the privately financed museum establishes its territory with a fortresslike presence. A protective, rusticated red-brick cloak wraps around three tiers of windowless blocks. Horizontal friezes of brick armor encompass the museum's massive rectangular base.

Centering this unsentimental building, a cylindrical oculus, banded in white and black granite, rises with its skylight focused above and away from the cityscape. Designed to bring natural light into the central interior courtyard, the oculus provides the identifiable feature of the museum's exterior, and rescues the building from starkness. It is emblematic of Mr. Botta's building that the primary source of natural light is also the central metaphor for his design.

The public entrance is both problematic and revealing. On either side of the main doors, a cafe and bookstore are logically sited - each welcoming to the visitor and obvious in their revenue-generating roles. But these are ancillary activities of the museum. For all that Botta has spoken about the museum as a gathering place, ``a receptacle for a collective consciousness,'' the cafe and bookstore face the street and have little connection to the interior piazza.

The actual entrance is spare and unwelcoming. A low black overhang, stainless- steel-clad side doors with ungenerous windows, and a central stainless-steel revolving door, confront the visitor just steps away from busy traffic. The reflective quality of highly polished steel creates a distorted image for anyone approaching. There is no place to linger. Visitors must enter the narrow revolving door alone.

Botta's humanity is only revealed inside the building. The central atrium is an extraordinary space, rising 135 feet, suffused with limitless vertical light, holding the visitor in immediate thrall. This is a radiant place, ecclesiastic both in its architecture and in its light, in what is built and what is left to the air. What Botta has accomplished here reminds one of a great actor whose silences are as commanding as the words he speaks. And it is Botta's resolution of structure, light, and space that has created a masterpiece for San Francisco's Museum of Modern Art.

A sanctuary from the outside world, the museum's emotional focus revolves around the central shaft of light. Botta's masterly handling of geometric form creates a graceful progression through space. That the journey leads heavenward is in absolute harmony with Botta's concept of museum as cathedral.

A grand staircase holds court on the eastern side of the atrium. Continuing bands of black granite frame a massive but low portal to the staircase. The refined and raw granite treatment continues up the core of the staircase. For all of its drama, the staircase is narrow, the granite stairs are rough and somehow humble. The journey into the galleries begins in a solitary walk rather than a grand parade.

As one moves through the museum, slowly spiralling upward, the manner in which the galleries are separated from general traffic provides an orientation to the anchor of light. It is a calm and meditative journey in Botta's reverential space.

The galleries along the perimeter are topped by deceptively simple skylights consisting of glass gables with metal-panel bases perforated at an angle, permitting only northern light to enter the double- curved plastic lenses. Botta has written, ``I like the thought that the artworks on display will be viewed through the `real light' of the city. With filters and veils, you can control and modulate light through skylights, thereby offering optimum conditions while also leaving the walls completely available as expository surfaces.''

The interior galleries, featuring daylight-sensitive photography and works on paper, have indirect artificial light emanating from fixtures designed by Botta.

Galleries are conservative and traditional, except for their size and flexibility. The sheer amount of space is breathtaking. Combined with the purity of the surroundings, there exists a peacefulness in the galleries, even when viewing defiant, often deliberately difficult and disturbing works of art. The galleries project a feeling of timelessness.

In the continual progression upward, the viewer's perspective is changed by the windows. Many are tiny, slit-like openings, framing exquisite miniature glimpses of the city and sky. Other windows create much larger portraits, often affecting works installed in front of them. Richard Serra's ``House of Cards'' appears to rest under the luminous moon of a Union 76 sign; a string of Bay Bridge lights becomes soft stars in the winter fog.

At the final clerestory reach of the journey, one can enter the cylindrical light of the oculus. A suspended bridge, 75 feet above the atrium floor, spans the diameter of light, allowing visitors to walk across. Breaking the spell at the moment it should be most exalted, the bridge violates the mysticism Botta has so carefully created.

* The museum opened Jan. 18.