For a century, the 48-panel stained-glass window loomed over a Rhode Island church congregation, its fantasy palette of pink, mauve, midnight blue and countless other colors slowing dimming through the years.

Now, the Tiffany Studios window sits in the basement of the Art Institute of Chicago, where a team of art restoration experts hunch over the scattered pieces, gently scrubbing away the grime and sealing tiny cracks.

In September, the window — the backdrop for a congregation of dozens at Community Church of Providence — will be seen by an estimated 4,400 people daily when it’s expected to be unveiled at the top of the Art Institute’s grand staircase.

Even in a city that’s home to plenty of spectacular Tiffany glass, including the Art Institute itself, the Hartwell Memorial Window is a rare find.

“This is absolutely just a breath-taking acquisition,” gushed Sarah Kelly-Oehler, Field-McCormick chair and curator of American art at the institute.

Tiffany Studios “glass house” in Corona, New York, produced some 5,000 windows at the beginning of the 20th century through the late 1930s, but most displayed purely floral or sacred themes, Kelly-Oehler said. The institute’s new acquisition shows a ribbon-like waterfall splashing into a pool surrounded by lush vegetation. Hazy blue peaks of New Hampshire’s White Mountains loom in the background. It was designed by Agnes F. Northrop, the studios’ leading landscape window designer.

The window was originally installed in the church in 1917, a tribute from a parishioner, Mary Hartwell, whose husband had died six years before.

Evan Howard, the church’s current pastor, could not be reached for comment. The institute quoted Howard as saying: “Our congregation decided to find a new home for the window, where it could be experienced by a broad public audience that includes scholars, artists and visitors from around the world. The church approached a number of different musuems and ultimately selected the Art Institute of Chicago as the ideal institution to care for and display the window.”

The window arrived in Chicago in July 2018. So why did it take so long to tell the public about it?

“We wanted to be at a place where we had firm plans for the installation of the window, and we’re also nearing completion of the conservation on the window,” Kelly-Oehler said. “Visitors to the Art Institute very soon will start seeing activity going on around the installation. It was word we wanted to get out.”

Kelly-Oehler would not reveal how much the museum paid for the piece, saying, “We don’t reveal information about artwork values.”