Rockefeller Apartments

Maybe they've been doing work. The co-op toddled along with a mortgage of less than $2,000,000 until the early 2000s, when it borrowed another $4,000,000+. Then earlier this year it borrowed another $18,000,000. That's pretty hefty for only about 200 apartments.

This says the $18,000,000 in new debt was for "various capital improvement projects": http://www.rew-online.com/2014/04/03/finance-briefs-eastern-navigates-market-like-gsp-23m-rockefeller-loan-cherry-hill-mortgage/

The building has taken on new debt to finance valuable and badly needed capital improvements.
The most notable has been replacing the 80 year old single pane steel frame windows with custom insulated and soundproofed double pane windows. Infrastructure also has been addressed this includes a complete electrical overhaul allowing for more electrical load capacity. Re-vamped hallways and a refreshed and improved landscape plan for the private interior courtyard park have also been initiated. The new windows will reduce the energy bill for the building dramatically.

Much of the borrowed money will be paid down with income provided by a windfall profit generated by the sale of existing air rights to neighboring properties.
The building is deemed an historic Art Deco landmark and is intimately tied into the development of Rockefeller Center and the subsequent founding of the MOMA. The building was built by the Rockefellers.
Apartments on the 54th street side of the building have a stunning unobstructed view into the sculpture garden of the MOMA and light pours in to the residences from the east south and north because there are no building s obstructing their views where the Museum is.

Weren't there one or more lawsuits over the window restoration?