Talk to the people who were there in 2004 and you can sense how poorly the the National Park Seminary in Silver Spring, Maryland, was faring.

Years of neglect had left the campus’ buildings—constructed between 1887 and 1927—nearing the point of no return. Leaking steam had rotted and ultimately collapsed some floors, vandalism had taken a toll, and parts of the facade were crumbling.

“From a condition standpoint it was horrible,” says Dave Vos, Development Project Manager at The Alexander Company, the developer behind the renovation. “It seemed like every time we opened up a wall there was another ‘I can’t believe what I’m seeing’ moment.”

Bonnie Rosenthal, Executive Director of Save Our Seminary—the preservation group whose decades-long effort ultimately rescued the architectural gem—puts it another way: “It was a great place for Halloween.”

But both Vos and Rosenthal knew there was something worth saving in the D.C. suburb. The campus’ eclectic mix of architectural styles (there’s a Japanese pagoda, Swiss chalet, Dutch windmill, and an English castle scattered throughout the Seminary’s 27 acres) and history made it something the area’s preservation community wasn’t going to lose without a fight.

It was first known as the Ye Forest Inn, a summer resort for D.C.’s elite designed by a young T.F. Schneider in 1887. But the inn never caught on and was converted into an all-girls school in 1894.

John and Vesta Cassedy introduced the international architecture, building eight sorority houses in varying styles during the early 20th century, hoping the students would be piqued by the physical space around them as well as in the classroom. As enrollment grew—topping out at about 400—so did the campus.

Several ownership changes later, the Department of Defense bought the property during World War II, renaming it the Walter Reed Army Medical Center Forest Glen Annex. For wounded soldiers, it was a quiet place for rest and recovery, though some complained that the buildings gave them haunting flashbacks to combat in Europe and Japan. It continued to house veterans of Korea and Vietnam until 1977.

But by the time Rosenthal discovered the Seminary driving around her new neighborhood in 1989, only a handful of the buildings were being used by the Army as office space, the remainder sitting vacant.

“There were days when I would go to the site and I would say, ‘Oh my gosh, there’s no way this place is going to be saved, it’s so bad,’” says Rosenthal. “And then the next day I’d go and I’d say, ‘There’s no way we’re going to lose this site, we’re going to save it.”

As the Seminary headed to the auction block, Save Our Seminary and affiliated preservation groups stepped in, brokering a deal by which Montgomery County would take ownership of the property and hand it off to a developer with certain guidelines for maximum possible preservation and some public access. When the deed was finally transferred to the Alexander Company, a preservation easement was attached, securing the Seminary’s stewardship.

For the company, which specializes in historic reuse, the renovation was a massive undertaking, ultimately costing about $120 million and leveraging more than $8 million in federal and state historic tax credits. Once the Seminary was converted into more than 200 residential units, it contributed roughly $60 million in property taxes to Montgomery County.

“It’s easily one of the most challenging adaptive reuse projects taken on—I can say this without reservation—in the country,” says Joseph Alexander, the president of the Wisconsin-based developer. “Had those buildings not been preserved when they were, they were almost too far gone to begin with and they most certainly would not have lasted if there was any further delay.”

According to Vos, it would’ve been almost impossible to pull off without the historic tax credits, which he says also helped construction businesses.

“Whereas you’d normally just want to rip out windows and replace them with windows that might be manufactured off site or somewhere else, you’re using a lot of local labor and employing a lot of people to renovate materials,” he says.

Rosenthal and Save Our Seminary’s roughly 230 members remain active giving tours, putting on lectures about the property’s history, and maintaining its extensive archives. A handful of buildings on the property are still awaiting completion, and the organization is working to restore all of the sculptures on campus.

Eager to keep the Seminary’s history alive, she encourages people to come and fall in love with it the same way she did, on a tour.

“It looks like it did in the early 1900s,” she says. “It’s like the Phoenix rising from the ashes.”