Dozens of bricks and chunks of limestone from the 11th floor of a long-vacant Park Avenue building came crashing onto the street in April. Nobody was hurt by the rubble that covered an area the size of an SUV, but it was an urgent reminder why Detroit officials had long considered the building a safety hazard.

Now, after decades of neglect, the historic structure at at 2001 Park Ave. on the edge of Detroit's Grand Circus Park — the last downtown building that officially had been designated "dangerous" by the city — has been stabilized by its new owner and taken off that list.

One week before pieces came raining down, the structure known as the Park Avenue Building was purchased for $4.9 million by an entity linked to a Novi development firm. The new owner promptly secured the property and since then has taken the first steps in an estimated $10 million to $15 million renovation for upscale rental apartments and ground-floor retail. Plans are to transform the 104,500-square-foot former office building into 75 to 100 apartments with 4,000-5,000 square feet of first-floor retail.

"Where you're standing, there was trash maybe up to your waist," said Rino Soave, the new owner, as he stood on the top floor of the Park Avenue Building. It cost $1 million to get rid of the trash in the 12-story building, said Soave.

"But look at these amazing views of the city from these great arched windows," said the owner and founder of Infinity Homes & Co. in Novi. "And these high ceilings; we're imagining two-story penthouses."

The planned revival of the building would mark a stunning turnaround in a city that gave rise to the phrase "ruin porn," referring to the tens of thousands of vacant, blighted properties that still plague Detroit. But in downtown — the 127 blocks bordered by the freeways and the Detroit River — the problem is almost history.

In 2010, the Park Avenue was among the 48 big, empty downtown buildings counted in an analysis by The Detroit News. Since then, billions of dollars have been invested into dozens of properties, reviving the once-bleak city core. The Park Avenue was one of the last buildings in the central business district that sat empty and neglected for years, if not decades, with no working development plan.

No one can recall when the Park Avenue last had a tenant; it's been at least 18, possibly 25 years. The building first opened in 1922 and was designed by Albert Kahn, often called the "architect of Detroit," whose work ranged from the Art Deco masterpiece Fisher Building in the city's New Center to the massive Ford Motor Co. Rouge complex in Dearborn.

The Park Avenue, briefly called the General Necessities Building, was originally designed for offices and retail. Like many Detroit buildings, it was hit hard by the mass exodus to the suburbs that began in the 1950s and continued for more than a half century. The plan to convert the building into residential is how many former office buildings downtown have found new life the past 15 years.

The Park Avenue was first declared a public threat by the city in 2002. That started a years-long legal battle with then-building owner Ralph Sachs. It was one of 40 downtown buildings the city targeted for legal action. That meant fines as high as $10,000 and, in some cases, lawsuits to get properties demolished or force owners to commit to extensive repairs.

In 2014, the Park Avenue was still "open, vacant and dangerous," according to a lawsuit filed by the city. "It is the very definition of irreparable harm to the public," the court filing said.

Brick and limestone weren't the only things that had the potential of falling off the exterior, the lawsuit charged. Portions of the fire escape were loose; shards of broken window glass fell on windy days. The ground floor had gaping holes that admitted looters and transients who further trashed the interior. Sachs did minimal repairs to stave off legal action, according to the city.

After Sachs died in January, his estate began to actively look for a buyer.

Soave had been looking for a downtown building five years ago but kept getting outbid. He was successful this time.

Part of the attraction of the Park Avenue Building was its "dynamite location," Soave said. Located just off Woodward, at the corner of Park and Adams, it sits on the on the same block as the historic Kales Building and Cliff Bell's jazz club in a burgeoning entertainment district.

Pieces of the exterior have fallen off, but plenty of neoclassical details remain. And while the 12 floors are marred with graffiti and broken fixtures, the concrete-encased steel columns are one reason the building foundation is solid, according to Laura Cunningham, an architect working with the new owner. Cunningham is a senior architect with the Detroit firm Kraemer Design Group, which has helped restore more than a dozen historic buildings downtown.

"I would say this building is probably in average condition compared to some of the other downtown buildings we have worked on," Cunningham said. "We helped restore buildings where floors were falling apart because the roof wasn't taken care of, and water was coming into the building, and sometimes there were trees on the roof."

With the Park Avenue Building off the dangerous buildings list, city officials could name no other downtown buildings with such a designation.

"Based on our most recent inspection information, there are no buildings in the central business district that are categorized as 'dangerous buildings,'" said David Bell, director of Detroit's Buildings Safety Engineering and Environmental Department.

Fewer than a dozen empty buildings remain downtown, according to several developers and others who keep track of commercial real estate. Most of those buildings have new owners who purchased the properties in the past decade and are either overhauling the properties now, or, have already done so and are actively seeking tenants.

"I'm glad we were able to buy this building," Soave said. "Because it was one of the last opportunities to get something like this downtown."

laguilar@detroitnews.com

Twitter: @Louis Aguilar_DN