San Francisco, which has only a handful of landmarked interior spaces, may soon have another: a small shop near Union Square designed by America’s greatest architect, Frank Lloyd Wright.

It’s located at 140 Maiden Lane, behind a dense wall of tan bricks pierced by a single deep arch. The facade is distinctive enough, but inside is Wright’s masterstroke — a spiral ramp to the second floor that predates his famed Guggenheim Museum in New York by more than a decade.

This is Wright’s only San Francisco building, one of his few surviving retail spaces, and a designated city landmark since 1974. When the larger-than-life designer died, the American Institute of Architects declared it to be one of his 17 essential works.

But the gallery also has sat empty since last summer, and now architecture buffs want to spell out what details must be protected before the next occupant starts making plans.

“We want to make sure that it’s clear from the start” which interior features can — and cannot — be altered, said Tim Frye, preservation coordinator for the city’s Planning Department. “This is such an important building in his overall body of work.”

Expanding landmark status

The department completed a draft report last month on how to expand the existing landmark designation to include aspects of the interior that date back to Wright’s 1948 design.

Besides the spiral ramp they include a sky-lit ceiling with 120 acrylic domes, a brass hanging planter and mahogany display cabinets.

Planners have discussed the unusual move with representatives of the owner, an affiliate of Hong Kong’s Gaw Capital Partners, and hope to send the stronger landmark designation to the Planning Commission and Board of Supervisors this spring.

A local representative of the owner could not be reached for comment. But the move has the strong support of such scholars as Paul Turner, whose book “Frank Lloyd Wright and San Francisco” will be published by Yale University Press in October.

“If anything, the inside is more important than the exterior,” said Turner, a professor emeritus of art at Stanford University. “It’s one of Wright’s most exquisite designs, and it’s almost exactly the way it was originally.”

By “originally,” Turner means when Wright embarked on one of his few renovations of an existing building, a bare-bones 1911 warehouse a half block from Union Square. Wright took on the project at the behest of clients V.C. and Lillian Morris, who had opened the V.C. Morris shop on Maiden Lane a decade earlier and hired Wright to design four houses for them, not one of which ever got built.

Whatever the origin, no other single building so effectively distills the essence of a career that stretched from the late 1880s until Wright’s death at age 91 in 1959.

The masonry cliff harks back to the Prairie-style homes Wright did for prosperous residents of Chicago’s suburbs, including the arch, which could be an homage to his early employer, Louis Sullivan. Inside, the bubbled skylight foreshadows the vaguely sci-fi trappings that run through the work of Wright’s final decade — including Marin Civic Center, which opened in 1961 and was proclaimed by Pulitzer Prize-winning critic Ada Louise Huxtable to be “his last great project.”

Before the Guggenheim

Back to Gallery S.F. move to protect interior of Frank Lloyd Wright building 3 1 of 3 Photo: See Special Instructions, SEE SPECIAL INSTRUCTIONS 2 of 3 Photo: See Special Instructions, SEE SPECIAL INSTRUCTIONS 3 of 3 Photo: Frank Lloyd Wright Foundation, Guggenheim Museum





And then there’s the spiral ramp — a hint of the corkscrew that defines the Guggenheim’s legendary atrium and the embodiment of Wright’s knack for gestures at once confounding and memorable. While that museum didn’t open on Manhattan’s Upper East Side until 1959, Wright conceived the design in 1943; the Morrises’ remodel offered a way to test the concept in real life.

“He saw an opportunity to explore the Guggenheim idea, a spiral ramp as the centerpiece of a space designed to showcase beautiful objects,” Turner suggested. “It’s like he was making a little model of it.”

The combination of the large ramp and the small details — including circular display niches along the ramp — explain why the interior inspires such protective emotions among preservationists and architecture fans. That said, the interior has been altered before. Many of the finishes had been exiled to the basement when Marsha Handley and her husband, Raymond, purchased 140 Maiden Lane in 1997 for their Xanadu Gallery. They promptly embarked on a loving upgrade and restoration that included consultations with Aaron Green, who worked with Wright on Marin Civic Center.

Gallery’s closing

Raymond Handley died several years ago, and Marsha decided last year to sell the landmark and close Xanadu because “after 43 years of operating galleries, it was time to simplify my life.” She expressed confidence last week that the new owner, whose portfolio includes Los Angeles’ landmarked Bradbury Building, “is very sensitive to the (Maiden Lane) building.”

According to Frye, there have been several tours of prospective tenants for 140 Maiden Lane during the past year, including a restaurateur and a European clothier. That’s what prompted the current move to strengthen the protections.

“Instead of having the same conversation over and over again, we figured it was best to spell things out,” Frye said.

San Francisco at last count has more than 260 designated landmarks. Some of them, frankly, are more dubious than distinctive. But Frank Lloyd Wright’s gallery is like no other building in the city — or the nation — and this architectural treasure deserves the strongest protections we can offer.

Place is a weekly column by John King, The San Francisco Chronicle’s urban design critic. E-mail: jking@sfchronicle.com Twitter: @johnkingsfchron