A major development site at 400 Fifth Avenue on the northwest corner at 36th Street is understood to be "in contract."

Lehman Brothers and Tessler Developments LLC., is selling the vacant lot and, according to an article in the New York Post, Bi & Di Real Estate SpA has agreed to buy it for about $200 million.

The article indicated that Lehman had previously commissioned plans by Gwathmey Siegel & Associates and such a project is listed on the architectural firm's website, without a rendering however.

The Post article said that "current plans" for the site call for a 56-story, mixed-use tower that would contain about 145,000 square feet of hotel space on its lower floors and about 323,000 square feet of residential space on floors 18 to 56.

Bi & Di Real Estate is based in Italy and has developed offices and resorts in Europe and in Cuba, but this is its first project in the United States.

The site has been cleared for several months and had been acquired by Tessler Developments LLC from The Chetrit Group for about $150 million.

The site is convenient to Lord & Taylor, several major computer and electronic stores, and Bryant Park and its central midtown location is convenient to the city's two major train stations. It is also close to the Murray Hill, Chelsea and Flatiron districts.

Gwathmey Siegel is known for its clean, modern design and its recent projects in the city include the curved, reflective glass tower at 445 Lafayette Street, the Windsor Park conversion project at 100 West 58th Street and the Superior Ink redevelopment in the West Village for the Related Companies.

A previous design for the site was prepared by Peter Magill of Skidmore, Owings & Merrill and that called for a low-rise based topped by a rectilinear tower of about 50 stories with a highly textured facade of undulating faceted elements and slightly angled windows.

For decades, the Empire State Building stood in splendid isolation. In recent years, however, a few mid-size towers have risen and the development of a tower on this site would be the latest tall neighbor to the Empire State Building. Its site is two blocks south from 425 Fifth Avenue, a quite tall, yellow-and-white, apartment tower and it is three blocks north of 325 Fifth Avenue, a 40-story condominium apartment building now in construction.

Darcy Stacom and Bill Shanahan of CR Richard Ellis represented the sellers and Howard Lorber and Dolly Lenz of Prudential Douglas Elliman are understood to have advised the buyers.

A check of the city's building records on the Internet revealed no change of ownership yet.