870 United Nations Plaza

860 and 870 United Nations Plaza are two real buildings and two separate cooperative corporations that share a single tax lot and a single city building number. That is unusual, it is not a data error, and it breaks a great deal of automated analysis.

The specifics. The whole complex — both residential towers and the six-story commercial office base beneath them — sits on block 1360, lot 7501, BBL 1013607501, condominium no. 2692. PLUTO carries that lot under the address of the office base, 866 United Nations Plaza, classifies it as commercial, and reports zero residential units on it, because the apartments sit inside condominium units rather than on the billing lot. The Department of Buildings carries one building identification number, 1040072, for 860, 866 and 870 alike, and the city's building footprint file records a single structure of roughly 413 feet on the lot. There is no separate BIN for the East tower and none for the West.

Where the two towers do separate is in ACRIS. Recorded instruments distinguish lot 9001 — 860 United Nations Plaza from lot 9002 — 870 United Nations Plaza, the two residential condominium units within the complex, with the office units carried across lots in the 1000s under 866. That is the cleanest line in the public record between the two buildings.

What that means for a buyer. Any valuation model, tax lookup, comparable set or building-level statistic keyed to BBL 1013607501 alone will pool 860, 870 and the commercial base into one record and will produce a number that describes none of them. The same is true of anything keyed to BIN 1040072. Use the ACRIS unit-lot distinction — 9001 for the West tower, 9002 for the East — when the record needs to be tower-specific, and treat any building-level figure attributed to "UN Plaza" as complex-level unless it says otherwise.

And it means the two cooperatives are genuinely separate. Each tower is its own apartment corporation with its own board, its own share schedule, its own financials and its own policies. Terms documented for the West tower do not bind this one, and the offering plan describes each cooperative's interest as the volume of air space its tower occupies above the shared base. The structure is unusual enough that your attorney should walk through how taxes, base-building costs and shared-amenity expenses flow into maintenance before you sign. The West tower has its own profile.

The East tower rises 38 residential floors in dark curtain-wall glass above the office base. Contemporary architectural criticism was divided — the complex was read as large and somewhat ungainly in massing, and as a lesser relation to the Seagram Building and the former Union Carbide Building nearby — but the same records credit it with materially improving the residential standing of the area. The slab's proportioning relies on the shallow piers on its long façades, and the architecture is in service of the glass: oversized windows and nine-foot ceilings are the interior signature, and the views are the product.

Lower floors were laid out at smaller room counts; the upper floors carry the larger simplexes; the top eight floors of the two towers hold the complex's 56 duplexes, with gallery-and-curved-staircase layouts and, in some, wood-burning fireplaces. Those duplexes are the trophy inventory. Six decades of combinations mean line-to-line variation is substantial, and renovation quality varies widely.

Operations run on site, with doormen, concierge and attended elevator service. Ask for the current staffing schedule, the reserve position, the underlying financing and its maturity, and the complex's façade and capital-work status — and ask for them from this cooperative's documents rather than from complex-level material.

• Ownership form: Cooperative. Board package and interview required.
• Pets: Permitted with board approval.
• Financing: Variable across the building; records cite limits from 50 to 75 percent. Verify for the specific unit before making an offer — this is the single term most likely to be misquoted at this address.
• Subletting: Board approval required. Confirm the current sublet fee and term limits.
• Pied-à-terre, LLC and foreign ownership: Less explicit in the open record; board discretion, historically accommodating given the international resident base. Confirm in writing.
• Trusts: Permitted, including a Qualified Personal Residence Trust.
• Flip tax: Confirm with the managing agent. Do not assume the West tower's schedule applies.
• Post-closing liquidity: Substantial reserves are customary at this complex.

Recent sales

Recent transfers 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 $868/sf (floor-adjusted) across 4 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 6.1% 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 1-01360-7501). 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 on co-ops is not officially recorded, figures shown are approximate.

The complex's resident register is among the most extensively press-documented in Manhattan. Names attached to 870 United Nations Plaza in the national press over six decades include the broadcaster Walter Cronkite, who at one point held three apartments in the building; the author Truman Capote; Johnny Carson; the actor Yul Brynner; the publishers Walter Annenberg and Katharine Graham; the television producer David Susskind; the philanthropist Mary Lasker; and David Koch.

Understand the shared-lot structure before you fall in love. One tax lot, one building number, two apartment corporations and a commercial office base underneath. None of it is a defect; all of it is unusual, and it should be walked through with counsel.

Verify every policy against this cooperative's documents. The two towers' terms are similar but not interchangeable, and the financing limit in particular varies by unit.

The views are structural. Price the exposure, not the building average. South and east buy permanence; west buys the Midtown skyline.

The duplexes are a separate market. Fifty-six of them across the complex, on the top eight floors, with layouts that do not exist below. Do not price them off simplex comparables.

The QPRT accommodation is real and worth confirming. For estate-planning buyers it is one of the building's genuine differentiators.

Calibrate the neighborhood honestly. The complex is its own precinct — driveway, garden court, playground and Peter Detmold Park adjacent — but the blocks around the UN are quiet at night and the nearest subways are a real walk west. Spend an evening on the block.

Sell the complex, then the tower. The Harrison and Abramovitz authorship, the UN adjacency, the driveway and lobby sequence and the press-documented resident history are complex-level assets. The East tower's own exposure profile and corporation are what differentiate the specific apartment.

Lead with the operating plant. The staffing depth, attended elevators and amenity stack are the daily product here and they survive any buyer's diligence.

Be precise about what is documented. Present policies, fees and financials from this building's current documents rather than from complex-level lore. Sophisticated buyers' counsel will catch imprecision, and the two towers do diverge.

Closing timelines are cooperative-standard. Six to ten weeks from contract through board approval to closing.

If you're considering 870 United Nations Plaza, also evaluate:

• 860 United Nations Plaza — the West tower of the same complex; identical architecture and shared plant, separate cooperative, generally the relative-value entry
• 845 United Nations Plaza (Trump World Tower) — the corridor's 2001 condominium alternative, with permissive condominium mechanics
• 425 East 58th Street (The Sovereign) — Emery Roth & Sons 1974; the closest post-war luxury co-op peer on scale and service
• 400 East 56th Street (Plaza 400) — 1968 post-war cooperative peer with a similar full-service program
• 45 Sutton Place South — post-war Sutton Place cooperative with river frontage
• 2 Sutton Place South — the pre-war trophy alternative on the river
• 1 Beekman Place — the corridor's old-line pre-war trophy cooperative; the prestige step-up