The richest residents of New York City are living in multi-million-dollar Frankenmansions

The Missionary Sisters of the Immaculate Heart of Mary, an NYC-based convent of nuns, acquired the townhome on the right in 1948. Four years later, the group bought the one next door and connected them via a doorway on each floor.

Throughout the years, the order has rented some of the complex's 25 bedrooms to other congregations or young women in need. But the Frankenmansion may soon find a new owner — the 15,600-square-foot space went on the market for $19.75 million in 2016, according to the New York Times.

The star of Sex and the City snatched the two brick townhouses above from the nonprofit United Methodist Women, then fused them together. The organization listed the pair of buildings (which were not connected) for $44 million in 2016, but Parker paid $34.5 million, according to The Real Deal.

The 13,900-square-foot mansion includes nine bedrooms, eight bathrooms, a 2,100-square-foot private garden, and five floors.

Sean Parker, the former president of Facebook, owns the three brownstones pictured above. Each building originally contained four apartment units, a grand stairwell, and a rear garden. The interior spaces feature arched doorways and original 19th century fireplaces with marble mantles.

Parker purchased the first building for $20 million in 2010, the second for $16.5 million in May 2016, and the third for a reported $22 million in August 2016. He completed the renovation to connect all three in late 2016.

Billionaire Jon Stryker is the rumored owner of the three brick buildings above, which NYC-based architecture firm Steven Harris Architects is working to turn into one residence. Curbed reported that Styker was probably the buyer of the $32 million set in 2012. The renovation project is still undergoing an approval process from the city.

In their former lives, the buildings were an ice cream factory, a Steinway piano showroom, and a garage. If the plans go through, the property's facade will stretch 41 feet from end to end.

In late 2016, Russian billionaire Roman Abramovich got approval to connect three townhouses on the Upper East Side, according to 6sqft. He purchased the buildings in 2015 for a reported $78 million.

The facades will be preserved, and the center house will become the mansion's main entrance after construction is complete. The interiors will be completely renovated, and the backyard will feature a private garden.

Owned by the billionaire Safra family, the two limestone townhouses above were listed for sale in 2015 as a trio with the building on the far right. The asking price was $120 million, but the owners are now asking $75 million for just the pair, which will likely be combined by its future owner, according to Curbed.

A total of 25,641 square feet, the soon-to-be Frankenmansion would feature 18 bedrooms.

Feinstein bought the townhome on the left for $3 million in 2004, according to The New York Times. A year later, the one next door went up for sale for $3.825 million, and Feinstein purchased, gutted, and renovated it to connect the two.

The finished product features 18 rooms, twin staircases, seven bathrooms, two bathrooms, eight fireplaces, a 25-foot-wide backyard, and two pagodas, which serve as outdoor living and dining areas. He put the mansion on the market for $17.9 million in 2013, but later decided to keep it.

In 2009, Madonna bought three connected townhouses on Manhattan's Upper East Side. The $32 million mansion features 13 bedrooms, a dance studio, multiple dining rooms, a 3,000-square-foot garden, two garages, an elevator, and a private gym, according to Curbed.