A granite-clad townhouse in Boston’s Back Bay neighborhood was designed by artist Louis Comfort Tiffany more than 100 years ago and is now considered the most complete surviving example of his vision of living.

The pale facade, with limestone mosaic panels and a stained-glass window over copper-clad double doors, is one of only two exterior spaces designed by Tiffany, the only one remaining intact.

The interior, with an oval staircase and an entrance clad in white marble and mosaic steps, is equally eye-catching.

Known as the Ayer Mansion, the building has been owned by nonprofit organizations affiliated with the Roman Catholic group Opus Dei for decades, and functions as part of a cultural center and residence for women attending nearby colleges. During this time, the doors were regularly opened for guided tours, lectures and concerts.

But all of that could change soon.

The mansion was recently put up for sale – along with an adjoining building – for a price of $ 22.5 million. This has caused a degree of distress in some people who have worked for years to restore what they consider to be a crucial monument to Tiffany’s genius.

Among them is Jeanne M. Pelletier, the conservation consultant for the nonprofit group Campaign for the Ayer Mansion, which has raised public and private funds and worked with the owner of the mansion to repair and restore some of its features. Pelletier said she and others were concerned that a sale could stop or lower the standards of these efforts and make the mansion, which is a national historic landmark, inaccessible to scientists and other visitors.

“Our greatest fear is that these nationally listed historic interiors will never be seen by the public again,” she said in an email, adding that it would be “a farce” for the public to have access to the “museum quality” of the city Losing building. Properties.

A spokeswoman for the Trimount Foundation, which owns the mansion and adjoining building that together make up the residence and cultural center, said the listing was for both properties and was due to lower tuition fees, which raised money to run them because of the pandemic.

Trimount, along with a group that operates the residence and center, would like to see what potential buyers could emerge, spokeswoman Marie Oates said, but would be willing to hold onto the property if they didn’t get an offer they were happy with .

Additionally, Trimount would love to find a buyer who appreciates the mansion’s history, Oates said, hoping that any new owner would open the premises to the public, although that would be difficult to guarantee.

“We want to prioritize a buyer or offer that has an interest in preserving a national treasure,” she said. “If we can find a buyer who allows public access, that would be great. We’d love it. “

Pelletier said Trimount’s director told her the mansion and adjoining building could be sold separately.

Alice Cooney Frelinghuysen, an expert on Tiffany who is the curator of American decorative arts Anthony W. and Lulu C. Wang at the Metropolitan Museum of Art, said the Ayer house was in large part remarkable because of almost all of its original features present are preserved.

Frelinghuysen said this included the modernist entrance hall, dramatic staircase, golden mosaic ceilings, favrile glass vases, and a trompe l’oeil temple on a landing, all of which together form a single ensemble.

“The Ayer Mansion is an extremely important preserved Louis Tiffany interior,” she said. “Everything was conceived as a whole work of art.”

The mansion was built between 1899 and 1902 for businessman and art collector Frederick Ayer as per the Ayer mansion campaign.

Since 1964, it has been owned, at different times, by two different nonprofits affiliated with Opus Dei, an influential group historically linked to right-wing concerns based on the premise that normal life and daily work pathways are for holiness and service to society.

The building was used throughout this time by a third non-profit organization, the Bayridge Residence and Cultural Center, which also has a connection to Opus Dei and promotes “moral and ethical integrity”.

Bayridge began restoration work in 1997, initially hiring an architectural firm to conduct a study of the mansion and draw up a conservation plan.

Since 1998, restoration work has been organized by the Ayer Mansion Campaign and an eponymous predecessor group that has received grants from the City of Boston, the Massachusetts Historical Commission, and the Federal Save America’s Treasures Program, as well as private foundations and donors.

Working with Trimount and Bayridge, the Ayer Mansion campaign saw nearly $ 3 million of indoor and outdoor restoration work completed. The campaign restored mosaic panels on the facade and repaired stained glass from the manor’s library.

It also restored a 20-foot-long Tiffany laylight above a marble staircase, using existing glass and replacing missing parts with rare surviving glass from the Neustadt Tiffany Glass Collection.