The project will include the development of seven full-floor condominiums and a penthouse duplex set above an existing commercial bank. There will also be an adjacent four-story townhouse, at 1281 Madison Ave., containing ground-level retail and four residential units for maid and/or nannies, according to a statement.

While construction is under way, a spokesperson for Sonnenblick tells GlobeSt.com that developers are still awaiting official project approval from the Attorney General. Developers are confident they'll get the go-ahead, the spokesperson says, at which time a construction timeline will be set in place along with asking prices for the luxury residential units. Currently, condos are estimated to sell for around $5 million to $15 million.

"Large condominium apartments of such high quality are very rarely available in Carnegie Hill," explains Mark J. Ehlinger, a director at Sonnenblick-Goldman. "Consequently, 47 E. 91st St. is certain to generate extraordinary demand from potential buyers."