The announcement on Monday that the Pritzker Architecture Prize went to Santa Monica architect Thom Mayne ought to stir things up downtown, where several big, slick, unimaginative projects are under way. Mayne is an unabashed radical, a founder of the eternally cutting-edge SCI-Arc and a designer of domineering, difficult forms. As Pritzker juror Karen Stein said, “Thom Mayne sees architecture as a contact sport — a group activity that pushes physical limits.” His signature Caltrans headquarters, at First and Main streets — the very crossroads of L.A. — embraces a gritty, unvarnished vision of the city. If Frank Gehry’s Disney Hall billows gracefully, like a spinnaker on Santa Monica Bay, Mayne’s Caltrans rumbles authoritatively, like a tanker on the high seas. Mayne regards the city — and downtown especially — as unsettled turf, always taking form. Hence his firm’s name, Morphosis, from the Greek, meaning “to be in formation.” “I’ve always had resistance to closed things, versus asking more questions,” Mayne told the Weekly after receiving the prize. “I am interested in the dynamic of building, of leaving the spirit of construction alive in the building.” That concept is anathema to our civic leaders, who suffer from an abiding inferiority complex and are always searching for ways to finish the city — rather than leave it open-ended. Scheme after scheme is trumpeted as the solution to what ails L.A., which is usually diagnosed as a city with no center or a center with no people. Nowadays, the accent is on the $1.2 billion Grand Avenue makeover (in which Mayne has been an on-again, off-again participant) and the new $300 million LAPD headquarters, Chief William Bratton’s land grab directly across the street from both City Hall and Caltrans. Each design could use a healthy dose of what has earned Mayne not only the Pritzker, but a raft of recent large-scale public commissions. Mayne, quite simply, challenges us to rethink our notion of a building — not only what it looks like, but how it stands in relation to its surroundings. Just have a look at Caltrans. The building, admittedly, has its failings, not least that its entire eastern fa?cade along Los Angeles Street is as impenetrable as a concrete gun emplacement. But on Main Street, the terms are very different. A large plaza is partially covered in a piece of the building’s pewter-toned perforated-steel cladding that appears to have peeled off and crumpled, as if it had encountered the pavement in a gargantuan fender-bender. From beneath that awning, you can look straight up into a void between the building and its metal sheathing. The flat scrim, held about one foot from the actual building, is not gala wrapping paper. It is a critical thermal blanket, like human skin, a movable, mutable layer that protects the interior from sunlight, reducing the building’s energy consumption by 20 percent. Mayne is forcing us to ponder the actual purpose of a building’s exterior wall, while upending the typical conventions of a steel-and-glass office tower. In his most celebrated work, Diamond Ranch High School, in Pomona, Mayne built a collection of angular, tilted fragments that become a canyon — contemplating the hillside landscape through a man-made image. The shopworn suburban campus, usually indistinguishable from the local Ralphs, has new meaning. It is from these works, and a number of other Morphosis projects, including the San Francisco federal building and the Eugene, Oregon, courthouse, that L.A. can learn to make bold architectural choices. For three decades, Mayne has held on to his independent voice. He’s stood his ground. He’s built tough buildings that defy easy categories. We should celebrate the Pritzker, and then we should get on with paying Thom Mayne an even greater homage: following his example.