The Zeckendorfs will ask $100 million for the top penthouse at their 88-unit condominium building, 50 United Nations Plaza, currently under construction in Turtle Bay. The 15,597-square-foot triplex at the Norman Foster-designed building is slated to have 14 bedrooms and 13 full bathrooms. The apartment also boasts 1,500 square feet of outdoor space and a 10,000-pound stainless steel staircase leading to an infinity pool, the New York Post reported. The building – which should be complete by December 2014 — is being developed by the Zeckendorfs as and Eyal Ofer’s Global Holdings. It is Foster’s first residential project in the country. Condos in the building, at First Avenue and 46th Street, will start at $2.8 million, as previously reported. The developers paid $160 million for the site in 2007.

The black building in the rear is Trump World Towers. It is about a block further up First Avenue.