MIDTOWN MASTERPIECE

MIDTOWN'S biggest development puzzle is a mystery no more. The image at right shows the first rendering of the West Side's most buzzed-over, blogged-about new skyscraper - Boston Properties' 1 million square-foot office tower at Eighth Avenue between 54th and 55th streets, to be known as 250 W. 55th St.

The design by Skidmore Owings & Merrill's Chris Cooper has not been previously released. It calls for a glass curtain-wall tower of 39 stories, set back from the avenue atop a graciously proportioned base boasting a 57 foot-high, wraparound glass retail façade and 25,000 square feet of stores.

Excavation and demolition of smaller buildings on the site are underway and Boston says tenants will be able to move into its new project by January 2010.

Publicly traded Boston, led by Mort Zuckerman, finished assembling the site last year, and real estate circles have mused ever since over its plans for the once low-rise block.

Boston bought the land from developer Robert Gladstone, who previously acquired it from Hearst and from a local family for a total of around $200 million. In a recent filing with the Securities and Exchange Commission, Boston pegged its total investment in the project at $910 million.

Law firm Gibson, Dunn & Crutcher has signed a lease for 220,000 square feet on its upper floors; a deal with law firm Proskauer, Rose for between 500,000 and 600,000 square feet is pending. CB Richard Ellis is the leasing agent.

To complete its assemblage, Boston is buying air rights from Broadway's Shubert Organization. Sources said that deal has received the blessing of the Department of City Planning, paving the way for the sale to go through and for construction to begin once the site is completely razed.

Eighth Avenue has now become an unlikely architectural showcase with recent completions of Sir Norman Foster's Hearst headquarters at 57th Street, Renzo Piano's New York Times Co. tower at 41st Street, and Arquitectonica's Westin Hotel at 43rd Street.

Meanwhile, Stephen Pozycki's SJP Properties' 40-story 11 Times Square, designed by FX Fowle, has begun to rise at the southeast corner of 42nd Street, and Jay Eisaenstadt is completing a 43-story condo at 47th Street designed by Ismael Leyva.

But until now, the Boston project remained shrouded in mystery as the company negotiated simultaneously with the Shuberts, prospective office tenants and a handful of residential tenants still living at the site.