The former Patterson Mansion on Dupont Circle is now Ampeer, a 92-unit luxury resident for “highly-transient” urban professionals. (Courtesy of Saul Urban/Courtesy of Saul Urban)

Remember when apartment buildings with pools and gyms were a big deal? Then real estate developers threw in flat-screen TVs and free wireless. Then concierge services.

And now: instant friends.

The latest entry in the urban rental market is not a tiny apartment in a hip neighborhood. It’s a tiny apartment in a historic mansion with like-minded housemates looking to connect with one another. In the platonic sense, of course.

That’s the concept behind Ampeer, the new luxury residences on Dupont Circle opening this weekend. The magnificent former home of newspaper heiress Cissy Patterson has been transformed into a 92-unit property for “highly-transient” urban professionals — people living in the District for just a few months, relocating to the nation’s capital or uninterested in conventional apartment living.

In addition to fully furnished apartments, residents get to hang out in the mansion’s gourmet kitchen, library and ballroom (where a private mixologist will serve drinks nightly) and bond over cooking lessons, author readings and other programs to keep them engaged and entertained.

“We are a hybrid between an apartment, a hotel and a social club,” explains Dan Rigaux, a senior veep at Saul Urban, which co-developed the building with Rooney Properties. “We have people using it as a pied-à-terre, we have consultants and contractors, we have people moving to the area who are going to use this as a launching pad. Our hope is that they find it so convenient and enjoyable that they will stay much longer.”

None of this comes cheap, of course. Starting at $2,800 a month, flats at the Ampeer are less than a room at a nice hotel, but more than many apartments in the area. It’s a $40 million gamble that short-timers are willing to pay top dollar not just to live in the heart of Washington, but to become part of it.

The original ballroom is now a shared living room, complete with a private mixologist and free hors d’oeuvres in the evenings. (Courtesy of Saul Urban/Courtesy of Saul Urban)

The original inspiration for Ampeer was the lonely businessman, bored and sad in the flickering blue light of the television, aimlessly flipping the remote in his soulless executive apartment. From that, the list expanded to graduate students, lawyers, diplomats or anyone weary of hotel living, regardless of who’s footing the bill. “I don’t know if you’ve ever lived in a hotel,” says Rigaux, “but it gets old really fast.”

The question is whether professionals are willing to pay as much or more for the added value of living with other grown-ups in a classy version of temporary housing. It’s the upscale sibling of dorms and cruise ships, where small rooms are used primarily for sleeping, and most of the fun stuff happens in communal spaces.

Unlike in dorms, the shared spaces here come with an impressive history. In 1903, renowned architect Stanford White built the 36,470-square-foot, four-story mansion for Robert Patterson, editor of the Chicago Tribune, and his wife, Elinor Medill Patterson. It was designed to impress, with curving staircases, marble fireplaces and glittering crystal chandeliers. The Pattersons’ daughter, Cissy, entertained Washington’s elite in the house and lent it to President Calvin Coolidge while the White House was being renovated. (A Warhol-like portrait of Cissy hangs in the library, which has been painted black and converted to an open office space.)

In 1951, the property was sold to the Washington Club, a private ladies’ social organization. It thrived for decades as an elegant meeting place for well-connected women, but maintenance costs and an aging membership forced the club to sell in 2014 for $20 million. The developers poured another $20 million into converting and expanding the mansion into Ampeer. (The name is a play on “ampere,” as in electricity, and “peer” — as in, well, your peers.)

The new design retains the classic exterior and the large public rooms, which got a facelift from Washington interior designer Darryl Carter. The original ballroom is now an elegant living room where residents and their guests can enjoy complimentary hors d’oeuvres and (not complimentary, alas) custom cocktails. The former dining room, which overlooks Dupont Circle, is a modern kitchen with a huge table where everyone gets a free breakfast or can host private dinner parties.

Upstairs, the original bedrooms and maids’ rooms have become 22 small one-bedroom or studio apartments; the new adjoining tower has another 70 studios. They’re Manhattan-size spaces — 350 to 600 square feet — in the ubiquitous beige of modern decor — and come with a bed, a couch, a TV, a mini-kitchen, sheets, towels, dishes, pots, pans, everything you need in a place you don’t plan to spend a lot of time in.

A portrait of Cissy Patterson hangs in the library, which is now a shared office space. (Courtesy of Saul Urban/Courtesy of Saul Urban)

A studio apartment in the mansion, with original windows and moldings. (Courtesy of Saul Urban/Courtesy of Saul Urban)

But the developers are banking that even short-term renters want more than just a room with a view. They want to meet people, have fun, explore the city. They want friends.

Hotels aren’t designed for guests to develop relationships. Apartment buildings these days have a long list of glossy amenities, but aside from workout rooms and pools, many aren’t big draws.

Corporate housing can command 20 percent to 30 percent more than traditional rentals, says Jon DeHart, an agent with Long and Foster, because executives demand convenience and a certain level of luxury. But their after-hours lifestyle hasn’t traditionally been part of the marketing.

Which is why Ampeer executives think they’ve found a void in the marketplace.

“It’s a fascinating model,” says DeHart. “It’s an opportunity for a real estate developer or owner to invest in a market that is very underserved. I think it’s really cool.”

After market research, company executives settled on a three-month minimum rental, with contracts accepted for up to one year. The target audience is people here for an extended stay. “Our offerings are intended to open up the city to them,” Rigaux says.

Ampeer is teaming up with local businesses and institutions — Politics and Prose bookstore, the Phillips Collection, restaurants — to bring in speakers, artists and chefs. There will be field trips to Nationals games and local distilleries.

There’s a premium for all these extras. For long-term renters, studios in the tower addition start at $2,800 per month, including all utilities. The same flats for three months? $3,422 per month.

The apartments in the mansion proper are more expensive because they feature many original design elements — molding, high ceilings, fireplaces, views of the circle. Studios start at $3,000 a month for a year and $3,667 a month for three months. The mansion’s six one-bedrooms (half are already rented) start at $5,200 per month for 12 months and jump to $6,600 a month for three months.

Rigaux says that short-term renters are responding to the social aspect, while longer leasers tell him that the all-inclusive prices aren’t dramatically higher than standard apartments in the neighborhood.

The developers are so confident of the concept that they’re already deep in the planning stages for another one in Shaw, on Blagden Alley, and are scouting a third location on Capitol Hill — and then, world domination.

Betting, of course, that people will pay more for a prefab social life.