Critically assessing Peter Zumthor's proposed 400,000-square-foot redo of the Los Angeles County Museum of Art'or indeed any major project in progress'is a risky enterprise. A sizable privately developed urban project that primarily serves the public tends to get people riled up. All that is much more so these days, since New York's Museum of Modern Art, of which LACMA might be a West Coast quasi-equivalent, has harmed its reputation because of two highly interventionist building campaigns, the first by Cesar Pelli in 1984 and one by Yoshio Taniguchi in 2004. Under no circumstances should the gigantism, commercialization, and appalling design judgment that has ensnared MoMA poison another major museum, and certainly not one as important as LACMA.

Designs are not buildings. Designs are not even half buildings. Designs are promises, flashbulbs of an idea. This past summer, Zumthor exhibited a newly revised design at LACMA, a black concrete-and-glass Rorschach inkblot of a building raised 30 feet off the ground, oozing this way and that around the La Brea Tar Pits, with one part bridging Wilshire Boulevard before landing in a parking lot across the street. However prematurely, we must still try to understand and assess this work, because it is surely one of this country's most important current civic projects.

How to proceed, then? By trying to understand Zumthor's design process, that's how. This happens to be a topic that he and I have discussed several times over the course of many years'most recently this past summer, at his exquisite country home in Leis, Switzerland, about a 90-minute drive (depending upon the strength of your stomach) from his office in Haldenstein.

Zumthor begins most projects with an in-depth analysis of the site, of which he builds one or more large models. From there, he works slowly, and he works iteratively: once, he told me that for the Swiss Sound Box pavilion (Expo 2000, in Hanover, Germany), it took him nearly two years to come up with the 22 'rules' guiding the design. The design concept is only a start. Zumthor revisits it repeatedly, rethinking the site plan and its program, considering multiple structural solutions, visiting and revisiting the circulation system and the configuration of the interior spaces. Then he rethinks it all again. Long after most architects of his stature (he won the Pritzker Prize in 2009) would have handed off drawings to design associates, leaving them mainly in charge, Zumthor is still thinking.

This can go on for some years.

Our recent conversation confirmed that whatever gets built will be different'indeed, might be quite different'from even the most recently exhibited drawings and models. Zumthor's central form-concept, however, is likely to hold: LACMA will be a single-story building, elevated off the ground plane. It will be black concrete, and it will bridge Wilshire Boulevard, a revision that was necessary to retain the museum's projected square footage while steering clear of the 40,000-year-old La Brea Tar Pits, an active excavation site.

For many baby boomers, trying to envision a large building elevated off the ground plane ignites memories of dank, shaded, desolate spaces beneath Corbusier-influenced pilotii-supported buildings. But Zumthor is thinking that LACMA will be high enough above the ground'30 feet is more than the upper range of Lina Bo Bardi's widely admired S'o Paulo Museum of Art. As for LACMA's projected color, I was concerned that a large flat, dark, elevated expanse of a building might feel forbidding, and so inquired why Zumthor had chosen black. In the past, he has maintained that his color choice is consistent with LACMA's goal of radically reducing the museum's carbon footprint, but, this time, Zumthor's reply reflected how determinedly he circles back over decisions, refining forms and details, rethinking it all. 'It might not be black,' he said with a wicked smile. 'It might even be white. In fact it was white'all last week it was white. But then I woke up one morning, and it was black again. And now I'm pretty sure that's right.' Limiting the building to one story ensures that the galleries will (or at least could) be illuminated by daylight, via skylights, and elevating that single story 30 feet above the ground makes the entire building into a sort of horizontal watchtower, enabling visitors to really see the city's horizon. It could change how we see Los Angeles even more than the High Line has changed people's perspectives on Manhattan.

The biomorphic form emerged, Zumthor explains, 'out of a long period of trial and error.' At the Kunsthaus in Bregenz, Austria (his first ground-up museum), Zumthor had already demonstrated his deft urban sensibility by splitting off the exhibition spaces from the bookstore, admissions, offices, and caf', placing them in a separate building. Together, the two buildings create a lovely little urban plaza, exquisitely scaled to the street and the city. But for LACMA, Zumthor explained, during the conceptual phase 'there were moments of despair because classical urbanistic patterns' could not pull together all the disaggregated components at Hancock Park'Piano's neoclassicizing buildings; Bruce Goff's idiosyncratic Pavilion for Japanese Art; the tar pits; the Page Museum; and the May Company Department Store to the west. The site needed a new focal point, Zumthor knew. But he wanted something 'soft on the edges, like a flower.' Were the tar pits an inspiration? Yes and no. 'Those tar pits are the soul of that site,' he declares. But he insists'even when pushed on the obvious isomorphism of the tar pits and the LACMA footprint'that the LACMA design does not represent the image of the feature, or anything else.

Critics wondering if Zumthor 'gets' Los Angeles may be asking the wrong question. The city matters, but so does the Ice Age site on which LACMA sits. Looking at art, Zumthor has said, can be a profound, even transcendental experience. For Los Angeles, Zumthor is less focused on the perpetual transience of the city than he is on the permanent'on what was there in Los Angeles before there even was a Los Angeles.

As for the interior galleries, Zumthor knows that sometimes the best way to absorb art is to be able to step away from it; that's one of the lessons from Louis Kahn's beloved Kimbell Art Museum and from the Yale Center for British Art. Zumthor intends to wrap the perimeter of the LACMA blob with a continuous, glass-enclosed ribbon of a veranda, varying its depth and the relationship of its walls to overhangs, depending upon view and geographic orientation. The result: in steamy Southern California, the veranda will offer climate-controlled public space, with yet more shaded public space below it. Users can come just to perambulate, taking in the scenery. Or they can use it to escape the art and look at the city spreading into the horizon. Or they can use it to escape Los Angeles en route to taking in the art.

Years ago, Zumthor told me how deeply impressed he was by the Process Art and Environmental Art that he saw exhibited in New York galleries in the late 1960s, when he was a student at Pratt Institute. His more recent work'the LACMA design, the addition to his own house and studio in Haldenstein, and the Brother Klaus Field Chapel in Germany'seems ever more inspired by the monumentality and land interventions of Robert Smithson, Richard Serra (with whom he is collaborating on a project), Robert Irwin, perhaps even Michael Heizer. For Zumthor, as for many of these land artists, architectural form is never the point. 'At the office,' he says, 'we never talk about form''a building's form emerges from the experience Zumthor aims to create. When you look at that Rorschach inkblot of a model, keep in mind that visitors will practically never experience the museum that way: only on a plane ride into town would anyone get that bird's-eye view. Zumthor is still working through the materials, the planning of the structural systems, entry sequences, and galleries. Everything he says about the LACMA design indicates that he expects this building to exude the emotionally rich, monumentally authentic presence of his celebrated spa for the Hotel Therme in Vals.

So what exactly can we be confident about in the LACMA design at this stage? The concept is thoughtful. The elevated horizontal plane will probably be fine, since it leaves enough space for Zumthor to shape the entrances and the plazas on the ground into appealing, functional spaces. Even the part bridging the boulevard will probably be fine. The site planning is brilliant: the museum will have as many as five entrances, which should disperse the oppressive cacophony of art-smitten masses that makes MoMA and other museums Bosch-like spectacles. The concept captures Zumthor and LACMA director Michael Govan's radical vision for what the museum-going experience should be. In Zumthor's organization of the interiors, no single work of art or collection will be presented, by dint of spatial hierarchy, as superior to others: they want the architecture to promote the feel of a democratic institution. They also want serene, contemplative galleries.

LACMA's concept dispenses with the visual histrionics of a Zaha Hadid or a Gehry. But this is entirely consistent with Zumthor's aesthetic. For LACMA and for Los Angeles, that may be a good thing. At least, it's not necessarily a bad thing.

And the recently revised footprint of the building is superior to the original. Tugging the inkblot's blobs farther apart not only sidesteps the tar pits but accomplishes two additional, highly desirable goals: it better integrates the existing Goff pavilion into the new design and breaks down the huge museum's exterior mass and vast interior spaces into smaller, more coherent connected spaces. The museum's various functions (art galleries; conservation and education; gift shop, restaurant, and entrance) and its collections (Asian and Pacific Art, European and American painting and sculpture, modern art, media, and design) would be housed in discrete nodes, each revolving around its own entrance. In four of these nodes the entrances are centrally placed, like a nucleus in a cell, and visitors will enter via a staircase wrapped into a glazed cylinder enclosing a sculpture courtyard. That way, users can visit just one node in the museum, leaving others for fresher days.

Will Zumthor's LACMA be the symphony that Los Angeles and LACMA's art collections deserve? It's too soon to know, especially as the design, like all Zumthor's smaller-scale, built projects, is driven much less by formal (one might even say photogenic) concerns than by sensory, tactile, visual, social, and associative experience. The human body and its experience of the environment remain Zumthor's core concerns. So we can be assured that this jump in scale need not necessarily affect the work's quality, since the human body's size, proportions, and much of its sensory experience remain the same, no matter how big the building. As for Zumthor's famous attention to architectural detail, he plans to open an office in Los Angeles next year, and to keep it open until the project is finished.

By the time I called Zumthor's office to check some of the facts in this article prior to publication, parts of the design had already changed. Zumthor is still thinking. But the day we spoke, he told me that each time he has to explain the project 'is another test of the design concept, for me to see if it is right.' So let's just let the man think.

Sarah Williams Goldhagen is the architecture critic for The New Republic.