A gestural ramp takes visitors to the upper stories, passing objets d’art nested into built-in niches. A bubbled skylight lets the sun’s rays penetrate into an expansive atrium, even on cloudy days. The AIA says the landmarked building is one of Frank Lloyd Wright‘s 17 essential works. The Guggenheim? Not so much.

Wright’s only San Francisco building, a city landmark since 1974, sits on Maiden Lane, a quiet side street downtown. The last tenant, Xanadu Gallery, closed up shop last year. Before the next tenant moves in, preservationists are rallying to expand existing landmark protections to include parts of the interior that date to 1948, including the ceiling, a skylit plane comprised of 120 acrylic domes, mahogany display cabinets, and a brass hanging planter.

Wright designed the project, one of his only renovations of an existing building, in 1948 for V.C. and Lillian Morris. The couple had a shop on the same street and had previously commissioned Wright to design four houses for them (none were built). The space became the home of the V.C. Morris Gift Shop.

Although the exterior, whose arch could be a subtle tribute to Louis Sullivan, is elegant, Wright experts concede that the interior is more architecturally significant. 140 Maiden Lane was a real-world test for the Guggenheim, built in 1959, which Wright conceptualized sixteen years earlier. The skylight hints at Wright’s later work, like the 1961 Marin County Civic Center. The Prairie-style homes Wright completed in the Chicago suburbs are echoed in the masonry cliff, muses John King, The San Francisco Chronicle’s urban design critic.

When Xanadu Gallery moved into the space in 1997, the owners, Raymond and Marsha Handley, restored many of the interior details that were left to languish in the basement. They consulted preservation experts, including Aaron Green, who with Wright collaborated on the Marin Civic Center. Marsha feels confident that the new owner, a Hong Kong–based investor who also owns Los Angeles’s Bradbury Building, will be mindful of this building’s significance. It’s rumored that the new tenant may be a restaurant, or a European clothing boutique.

City Planners have broached the bid for elevated landmark status with the owner’s representatives, as they intend to send the revised landmark designation to the Planning Commission and Board of Supervisors in the next few months.