Several converging factors - New York City’s continued economic and cultural growth, record-setting condominium sales, a renewed appreciation of the city’s historic buildings, and maturation of the residential conversion market - blessed past the decade with the most spectacular condo conversions in the city’s history. Some of the city’s most rarefied hotels (the Waldorf-Astoria, The Plaza), office buildings (the Woolworth Building, 100 Barclay Street, 108 Leonard Street), and even miscellanea such as schools (555 West End Avenue) and printing facilities (The Puck Penthouses) have become some of the most luxurious and most unique condominiums in the Big Apple, each uniquely adapting to the special character of their respective buildings.

See below for CityRealty’s picks for the 15 best conversions of the decade and some of their most intriguing condominiums currently on the market.

Originally opened as as the Hotel Chastiagneray in 1900, and located in what is now the Expanded Carnegie Hill Historic District, The Wales was designed by architect Louis Korn in the neo-Renaissance style and presents an uplifting stone-trimmed Roman brick facade and a lavishly-detailed entryway with a marble-stepped staircase. The hotel's name changed several times over the decades, but was known as the Hotel Wales when Adellco bought the building in December 2018. It quietly closed a year later and gave the last guests pieces of the hotel's historic memorabilia.

Much to the relief of local preservationists and architecture aficionados, historic details like terra cotta window surrounds, terra cotta joints, and the brick and limestone facade were restored to their former glory amidst the Landmarks-approved conversion to a condominium. The most noticeable change is a new cornice and penthouse with a wraparound terrace and roof terrace. The penthouse and all other units have interiors by Cabinet Alberto Pinto as well as access to amenities like an attended lobby, fitness center, and pet grooming station.

One Prospect Park West was originally built in 1925 by the Knights of Columbus. Members were treated to a ballroom, restaurant, bowling alley, billiards hall, indoor pool, and club rooms; also in its heyday, the Classical Revival-style building served as the social center of Park Slope. In its current incarnation, the facade was carefully restored while the interiors were transformed into apartments and amenities designed to meet the needs of today's buyers. All units feature arched entryways, reclaimed pine hardwood flooring, kitchens with marble countertops and appliances by Wolf and Sub-Zero, and marble baths. Residential amenities include a private curated art gallery, fitness studio, bike room, library, rooftop terrace designed by ODA, and elegant residential lobby inspired by the architecture of the 1920s.

108 Leonard Street is a dazzling 19th-century loft built in 1898 for the New York Life Insurance Company. The National Register of Historic Places-listed building was designed by architects S. D. Hatch and McKim, Mead, and White in an ornate Beaux-Arts style, complete with a four-sided clock tower facing Broadway. In 2019, architects HLZA and SLCE restored the landmark to its former glory and equipped it with features such as an opulent, double-height lobby, an indoor pool, and a roof garden. Arched windows look out onto Tribeca, one of the city’s most sought-after neighborhoods.

One Hundred Barclay Tribeca is a pre-war landmark located at the junction of the Financial District, Tribeca, and Battery Park City. Designed by Ralph Walker, dubbed “Architect of the Century” by the American Institute of Architects, and completed in 1927, the building was one of the city’s first Art Deco skyscrapers. The opulent Jazz Age lobby is one of the finest in all of New York. In 2015, the tower’s upper floors were retrofitted as sprawling loft residences with high ceilings and high-end finishes. Residences begin at 170 feet above street level, and rise from there, featuring ample light and views from the Hudson River to the Midtown skyline. The One World Trade Center rises across the street and comes into direct, dramatic view from south-facing apartments.

One Hundred Barclay boasts over 40,000 square feet of amenities that include a 24-hour doorman and concierge, a fitness center designed by The Wright Fit, an 82-foot lap pool with adjacent children's pool, and spa and treatment rooms. The club level on the 18th floor offers a billiards room, a club lounge with bar and dining room, a children's playroom, a teen lounge, a media lounge, a wine tasting room, music practice rooms, and four outdoor terraces. The building also offers bicycle parking and private storage and five-minute walking access to the shops at Westfield World Trade Center, Fulton Center, and Brookfield Place, as well as the parks and waterfront promenade at Battery Park City.

The Puck Building at 295 Lafayette Street in SoHo, one of the city’s grand 19th Century buildings, is distinguished by two gilded statues of Puck, a character from Shakespeare’s “A Midsummer’s Night Dream.” The full-service boutique residence with a 24-hour doorman consists of just 6 spectacular apartments atop a mixed-use building.

In summer 2021, The Wall Street Journal announced that Karlie Kloss and Josh Kushner were in contract to buy a sprawling penthouse in the building with 7,241 square feet of interior and 5,158 square feet of exterior living space, a library, a gym, a home theater, a wine cellar, and a landscaped private terraces with a yoga lawn, putting green, spa tub and wet bar. They also listed the other penthouse they owned in the building, which was developed by his family's eponymous firm.

555 West End Avenue is a masterwork of pre-war, Collegiate Gothic architecture, built in 1908 as a private school. The red brick facade is adorned with white stone trim, quoin window surrounds, owl gargoyles, crenellated turrets, and other touches that lend the building a majesty at once bespoke and magical. The school’s unique features were perfect for its 2019 conversion into 13 condominiums. Soaring ceilings and tall windows are as well-suited for classrooms as they are for high-end living. A stately sidewalk moat lends an equal degree of privacy and separation from the sidewalk for classrooms and condos alike. The arch-windowed library became an atrium-like living room with a second-floor viewing gallery in a 3,463-square-foot Library duplex. At the top, the vault truss-roofed basketball court transformed into a spectacular Solarium penthouse, lit by a massive skylight and a sheer window wall that opens onto a 37-foot-long private terrace.

The conversion also introduced luxuriant features such as a round-the-clock attended lobby finished in travertine, Calacatta Crema marble, white oak, and brushed bronze; a fitness center that looks out onto the rear courtyard; and an oak-wainscotted rec room with a bar, billiards, darts, and a large-screen TV. In the units, white oak and marble finishes create a light-hued theme that carries through the living rooms (herringbone-pattern wood floors), kitchens (counters, backsplashes, and cabinetry), and bathrooms (vanities, wainscot walls, and mirror cabinet trim). The building stands on stately West End Avenue, just a block away from the Hudson River-adjacent Riverside Park and a few blocks west of Central Park; the 86th Street station (1/2 trains) sits a block away.

Since 1907, the Plaza has reigned as the world’s most famous hotel, attracting global elites and garnering stories and myths for more than a century. In 2007, much of the legendary chateau was transformed into luxury condominiums, where residents can take advantage of the hotel amenities while enjoying pre-war opulence and direct Central Park views. Residents have access to the hotel’s notable restaurants – including the famous Palm Court – as well as its Caudalie Vinotherapie Spa, the Warren-Tricomi Salon and a La Palestra fitness center. Additionally, the Plaza offers such amenities as a 24-hour concierge and doorman, nanny service, limousine service, turn-down service and a private butler.

The Plaza faces the Grand Army Plaza at the intersection of Fifth Avenue and Central Park South, arguably the most prestigious address in all of New York City if not the world. The building sits within steps of Fifth Avenue’s high-end shopping, numerous corporate and entertainment destinations of Midtown, and within walking distance to shopping and dining at the Upper East Side.

Designed by Schwartz & Gross and built in 1913, the 21-story former office building at 212 Fifth Avenue facing Madison Square Park now holds 48 residential condominiums, with an ornate Neo-Gothic facade restored by Helpern Architects. The pinnacle holds The Crown, a three-level penthouse purchased by Amazon founder Jeff Bezos, who now owns $119 million worth of real estate in the building following additional purchases.

Pembrooke & Ives decked out the high-ceiled interiors with hardwood floors, while the architects added windows on the south side to provide extra sunlight and views of Madison Square Park into upper-floor units. Amenities include a 24-hour doorman, concierge, a Jay Wright-designed fitness center with a yoga studio and private treatment room, a golf simulator, a screening room, a boardroom, a game room, a children's playroom, a lounge and cold storage for fresh food deliveries. Storage rooms and staff quarters are also available for purchase.

The 15-story, Beaux Arts-style building at 49 Chambers Street, the former home of the Emigrant Industrial Savings Bank, was designed by Raymond F. Almirall and built across from the Tweed Court House in City Hall Park 1912. Over a century later, in 2018, the building was converted to 99 condominium apartments in 2018.

Luxurious amenities at 49 Chambers include a landscaped roof deck, swimming pool, hammam and spa, sauna and steam rooms, state-of-the-art fitness center, resident lounge, screening room, children's playroom, tween lounge and resident storage. Additionally, in September 2022, digital art museum Hall des Lumières opened in the Landmarks-approved conversion of the bank hall with inaugural exhibit Gustav Klimt: Gold In Motion.

The Belnord condominium on the Upper West Side occupies the entire block between 86th and 87th Streets and Broadway and Amsterdam Avenues. A local and nationally-designated landmark originally built in 1908, the building’s transformation was helmed by famous New York architect Robert A.M. Stern, whose unique talent for combining Gilded Age glamour with 21st-century luxury is evident in the reborn residence. The development is built around a lush, landscaped courtyard with a large central fountain surrounded by wide walkways, as could be seen in Hulu hit Only Murders in the Building. At 14 stories high, it has 215 two-to-six-bedroom apartments within.

30,000 square feet of indoor and outdoor amenities include a 24-hour attended lobby, expansive porte-cochère, and 22,000 square foot courtyard and garden. The two-story Belnord Club includes a state-of-the-art fitness center, a double-height sports court, a club lounge with a fireplace, dining room, children’s playroom, and teen room. Situated between Central Park and Riverside Park in the heart of the Upper West Side, the Broadway Corridor location is one of the most sought-after in Manhattan. The 1,2 subway lines are steps away at 86th Street.

The 22-story Walker Tower takes its name from Ralph Walker, the architect of the 1929 telephone switching building that comprises the lower floors. The architects at Cetra/Ruddy not only treated the original’s Art Deco with utmost deference, but also extended and intensified the energetic theme to create a 21st century masterpiece wrought in the finest Gotham style.

Building amenities include a 24-hour doorman, concierge, lounge, refrigerated storage, playroom, bike storage, gym, sauna and a roof deck.

Thanks to its underground parking garage (complete with electric charging stations) and prime north Tribeca location, 443 Greenwich Street has become a hot spot for celebrities, including Jake Gyllenhaal, Meg Ryan, Justin Timberlake and Jessica Biel, and The Weeknd, to name a few. The red-brick building was originally constructed in the 1880s as a book bindery warehouse but was converted to 53 condos in 2014 by the team at CetraRuddy, who also restored the landmarked façade.

The apartments are distinguished by historic features such as large, arched windows and restored wooden beams, alongside modern amenities and finishes. Amenities include a 71-foot indoor swimming pool, huge roof terrace, fitness center with private studios and an adjacent Hamman, and a 4,000-square-foot interior courtyard.

One Wall Street is one of the finest pre-war condo conversion developments in all of New York City. During the Roaring Twenties, the Irving Trust Company, then the nation’s fifth-largest bank, assembled a site at the Financial District’s premier intersection; by 1931, the bank erected its 50-story, 654-foot-tall headquarters, then the tenth-tallest building in the world. Architect Ralph Thomas Walker, dubbed “Architect of the Century” by the American Institute of Architects, wrought the tower in an understated yet opulent Art Deco style, with walls of undulating limestone, a cavernous Red Room ground-level banking hall clad in red-orange-gold mosaic, and a matching White Room clad in mother-of-pearl seashells in the beacon-like pinnacle.

In 2020, Macklowe Properties converted the designated city landmark, together with its 28-story annex built in 1963, into 566 luxury condominiums of varying sizes, many featuring unique layouts, lofty terraces, and spectacular views of the skyline and the harbor; the iconic Trinity Church and its grounds, located across Broadway to the west, mean that every west-facing unit, even those on the lower floors, boasts open views and ample sunlight throughout the year. The 176,000-square-foot amenity suite features a two-level space on the 38th and 39th floors with a 75-foot indoor pool with panoramic floor-to-ceiling windows on three sides, a fitness center that overlooks Wall Street and the World Trade Center, several lounges, and a two-level landscaped terrace. The White Room is now the centerpiece of a one-of-a-kind penthouse, and the Red Room will be home to the first United States outpost of French department store Printemps.

The Towers of the Waldorf Astoria is the conversion of the top floors of one of New York’s most legendary condominiums into 375 condominiums. Beijing-based Dajia Insurance Group Co. is renovating the 1931 landmark with interiors designed by Jean-Louis Deniot and an art collection curated by art collector and auctioneer Simon de Pury. Amenities will include a private porte-cochere, an 82-foot lap pool, a fitness center with men's and women's wellness lounges, a Grand Salon, and Starlight Lounge and Terrace. The hotel is also being restored and upgraded, with iconic landmarked interiors, such as the West Lounge, Grand Ballroom, and the Park Avenue lobby, restored by the esteemed architecture firm Skidmore, Owings, & Merrill.

The copper-clad pyramid roof atop the Crown Building has graced the corner of Fifth Avenue and 57th Street since 1921. Almost a century later, the ornate edifice has been reborn as Aman New York Residences, a bespoke addition to Billionaires’ Row. Owners of the twenty upper-floor condos may indulge in the services of the in-house hotel, which include a pool-equipped spa, a subterranean jazz club, a piano bar, a cigar bar, and a wine library. The penthouse offers a terrace with and outdoor pool and views of Central Park.

If the penthouse closes for the $180 million asking price, it will be among New York's most expensive real estate sales. In the meantime, it was home to the two most expensive sales of the third quarter of 2022.

Architect Cass Gilbert traveled across Europe’s medieval cities to draw inspiration for the Woolworth Building, a 1913 Neo-Gothic masterpiece. Though the 792-foot skyscraper no longer ranks as the world’s tallest, the beloved landmark continues to evoke awe and admiration. In 2018, the slender upper portion was converted into 33 elite condominiums.

Arched windows look out through colorful terra-cotta niches onto the Downtown skyline. The wide setbacks have become twin courtyards-in-the-sky, surrounded by parapets of cusped tracery and copper finials. At the top, the former observatory and the copper-clad pinnacle house a stunning, multi-level penthouse. Of the amenities - a wine cellar and tasting room, 29th floor lounge, and 30th floor fitness center - the most impressive is the restored 50-foot basement pool, which was originally commissioned by F.W. Woolworth himself.