On a brisk Saturday morning last week, Adam Kushner anxiously glanced outside his door on Minetta Lane, where an orderly queue had begun to form on the sidewalk.

Teeming crowds are not unusual on this quiet Greenwich Village block, which has an Off Broadway theater, a couple of restaurants and a music club. This time, though, they were waiting for a free tour of the 1929 townhouse that Mr. Kushner, the founding principal of the architecture and design firm Kushner Studios, had been painstakingly renovating for more than a decade.

“I would have been so mad if we missed this,” said Tessa Carter, a Washington Heights resident who had arrived an hour early with her friend Kristin Toth. They had always wanted to see the design of the space, but had given up in past years when they saw the size of the line.

Ever since Mr. Kushner, 62, bought the five-story house for $3.75 million in late 2012, it has been one of the most in-demand destinations at Open House New York, the annual citywide architecture festival that allows real estate gawkers to do more than just peek into windows. And this was probably their last chance: Mr. Kushner plans to sell the house before the end of the year.

More than 6,000 visitors have traipsed through the townhouse for a look at one of Manhattan’s most eccentric home makeovers — including the wood floors that Mr. Kushner made from felled trees; a rooftop lounge and kitchen with views of One World Trade Center and the Empire State Building; nine working fireplaces; a bar outfitted with 251 vodka bottles; and an 83-foot rock-climbing wall, believed to be the world’s tallest in a private residence.

When he bought the building, which had been a showroom and living space for the party designer Robert Isabell, it was meant to be a home for his family of four. But there were few family-friendly amenities. Some of his friends urged him to tear it down and start over, but Mr. Kushner was intent on preserving some core features.

He maintained Mr. Isabell’s skylights over the solarium and rear carriage house, and incorporated the original angled roof line into the fourth-floor outdoor space. In the courtyard, Mr. Kushner, an avid climber, erected the plexiglass-paneled climbing wall, giving his kids some vertical adventure without leaving the house.

“I would like to think that Robert would have approved,” he said.

The timing of his purchase was fortuitous. When he brought a project proposal to the city’s Landmarks Preservation Commission in February 2013, an official informed him that a chunk of Greenwich Village, including his home, would soon receive landmark status. “She conveyed to me at the time, ‘You should get your permits ASAP, because right now it is your house but soon it will be mine,’” he said. “I appreciated her honesty.”

The renovations didn’t always go smoothly. Mr. Kushner recounted how it took him two years to design his downstairs sauna, then grout and paint it by hand, only for water to seep under wooden discs and ruin the floor. On Christmas Eve in 2020, two scaffolding planks from a neighbor’s project smashed through an original skylight. The repairs took 18 months.

With the project finally complete in 2022, and after Mr. Kushner and his wife, Louise Chuu, sent their twins off to college the next year, they put the townhouse on the market for $20 million in 2024. After failing to find a buyer, they aim to list it again this fall.

But first, he wanted to share his vision and maybe even inspire his neighbors one last time. “For me, it is a complete love-fest,” he said. “I open the most personal aspects of my life and my family’s lives to the public, I put us all at risk, and yet 99.99 percent of them show me equal respect and appreciation and dare I say, love.”

On Saturday, Mr. Kushner asked some Open House volunteers to sign in visitors and monitor different floors. Only 25 people would be allowed inside at a time over the course of six hours. By day’s end, 268 people had checked in. “I have to limit it otherwise it’s going to be unruly,” he said. “In all the years we’ve done this, we’ve never had a major problem. Someone knocked over a pot last year, but no one has stolen anything.”

At 11 a.m., the first group poured inside. Some had traveled from as far away as Europe, including Luís Vega, who had timed his flight from Portugal so he could attend O.H.N.Y. events. “I loved it,” he said of the house. “If I could live here I would.”

Others were Village denizens curious to get a look inside their neighbor’s house. Elizabeth Baltusnik, who lives across the street, had caught glimpses of the climbing gym from her roof. “I figured if there was a rock-climbing wall, there was going to be something else interesting going on,” she said.

She left impressed by the wood detailing and the fireplaces. “There’s just so many of them,” she said.

Another neighbor, Anke Frohlich, jerked her neck upward as soon as she stepped into the courtyard. “Oh my God, the climbing wall! Amazing!” she said. “That’s a really tall wall.”

Mr. Kushner often recognizes repeat Open House guests, some of whom have monitored his progress and questioned why it took so long. One visitor told him she had first toured the home over a decade ago, when he started construction. “She said, ‘You had us walking across steel I-beams on the roof and it was dangerous,’” Mr. Kushner said. “That probably doesn’t sound so smart in hindsight.”

By 2 p.m., the line was stretching toward Sixth Avenue. Mr. Kushner allowed another dozen people inside to watch a slide show about the home’s history. Madeley Rodríguez and her husband were waiting for nearly two hours and just made the cutoff.

Ms. Rodríguez especially appreciated the natural touches, like the stacked wood wall in the living room and ivy-wrapped trestles on a terrace sunroom. “It’s a very different house from the way we typically live,” she said. “He brought nature indoors.”

When the house finally sells, Mr. Kushner will miss hosting hundreds of strangers once a year. “This is way deeper than seeing what a big house looks like from the inside,” he said. “When am I ever going to meet such a cross-section of New Yorkers and share some commonality between us?”