655 Sixth Avenue (The O'Neill Building)

The facade is the asset the district protects: five stories of cast iron painted to read as stone, organized in Corinthian bays with taller, broader glazing on the lower three floors — the legible DNA of a department store designed to flood selling floors with light. The two penthouse levels sit back from the street wall, deliberately subordinate; the restored corner domes carry the silhouette.

Inside, the 49 residences run from one-bedrooms through three- and four-bedroom lofts approaching 3,000 square feet, with the five duplex penthouses above. The signature inventory is the corner lines, whose living spaces wrap the window-banded curve of the towers — and the penthouses, where the largest spans roughly 4,800 square feet inside with some 2,500 square feet of terraces, including a bonus room inside one of the domes itself. Ceiling heights, column spacing, and window scale are genuine 1887 loft fabric; the finishes are conversion-era and have been re-renovated in many units since.

Full-service condominium: 24-hour doorman and concierge, live-in-superintendent-scale staffing, private storage, central laundry plus in-unit washer/dryers per listing records, and the landscaped roof deck with outdoor kitchen. The retail base is a separate commercial condominium unit — residents do not carry the retail space, but should understand the commercial unit's voting and cost-allocation framework in the by-laws. The offering-plan amendment set on file in The Roebling Research Library documents the conversion's certificate-of-occupancy history, early budgets, and unit changes; it is the right starting point for attorney diligence.

Recent sales

Recent closings at this building, from The Roebling Research Library. Prices are the transfer amounts recorded with the NYC Department of Finance; apartment-level detail is checked against the building’s own file in The Roebling Research Library before publishing.

Market read. Most recent trades (2026 to date) cleared a median $1,747/sf (floor-adjusted) across 3 sales. Floor-adjusted means each sale is restated to a constant mix of floors, so the figure can differ from the plain median of the sales listed above. Median listing discount 2.9% from the last ask — a recurring negotiation gap worth pricing into any offer or listing strategy.

Sales sourced from NYC Department of Finance recorded transfers (BBL 1-00796-7504; each condominium apartment is its own tax lot). Apartment-level facts (line, condition, asking-price context) curated and cross-verified in The Roebling Research Library. Not all transactions cross-verify with ACRIS records — sponsor and LLC purchases sometimes record at stipulated values rather than market price; square footage from recorded condo declarations and offering plans.

• Mariska Hargitay — the Law & Order: SVU star bought a duplex penthouse at the building in 2007 and sold it in 2008, a transaction covered by the real estate press; the unit's later listings drew coverage from Robb Report and Fox Business

You are buying protected fabric. The Ladies' Mile Historic District covers the facade, the domes, and the streetscape; exterior alterations run through Landmarks. Designation requires applicable preservation review but does not guarantee unchanged neighboring development or views; confirm permits for proposed window or envelope changes.

The corner lines are the building. Compare wrapped turret rooms and mid-block lines using their actual dimensions, exposure, condition and dated matched sales rather than assume exclusivity or a fixed price discount.

Condo mechanics differ from a co-op's. There is no co-op board interview; purchases run through the condominium's application and right-of-first-refusal process. Confirm trust, LLC and pied-à-terre rules in the current declaration, bylaws and house rules with the managing agent and your attorney.

Read the conversion documents, not just the listing. The amendment set on file documents the penthouse combination, the certificate-of-occupancy sequence, and the early budget reset (a 24 percent common-charge increase in the first resident-board year). Two decades on, the relevant question is the current budget and reserve posture — have your attorney review the latest financials alongside the historical record.

Mansion tax applies at nearly every price point here. Run the Mansion Tax Calculator at the intended price and understand the thresholds before you negotiate.

Market the narrative with precision. Hugh O'Neill, 1887, Merritt's cast iron, the demolished-and-regilded domes, the cemetery air-rights deal behind the penthouses — this is the best-documented story on the avenue, much of it carried in The New York Times. Buyers in this tier respond to verifiable history, not adjectives.

Position against both Chelsea and Flatiron. The building sits on the seam, and the buyer pool cross-shops loft conversions on both sides of Sixth Avenue plus the newer Flatiron towers. The pitch is singularity: full-service staffing and a roof deck inside an 1887 cast-iron landmark district building — a combination the comps cannot replicate.

Anchor to line-specific history. The spread between tower corners, penthouses, and mid-block lines is wide; building-average price per foot will misprice your unit in either direction. Same-line trades are the anchor.

If you're considering 655 Sixth Avenue, also evaluate:

• The Cammeyer (650 Sixth Avenue) — the converted Ladies' Mile shoe emporium directly across the avenue; the closest like-for-like
• Chelsea Mercantile (252 Seventh Avenue) — the neighborhood's large-scale loft conversion benchmark, one avenue west
• 141 Fifth Avenue — domed pre-war conversion on the Flatiron side; similar crown-and-cupola character
• 15 Union Square West — the former Tiffany & Co. cast-iron building reimagined as condos; the conceptual peer two squares east
• 212 West 18th Street (Walker Tower) — Chelsea's top-tier pre-war conversion; the price-ceiling reference
• 45 East 22nd Street — the new-construction Flatiron tower alternative for buyers weighing loft character against amenity depth
• The Grand Madison (225 Fifth Avenue) — large-floor-plate pre-war conversion on Madison Square; the NoMad-side alternative