11. 399 Park Avenue $1.06 Billion

399 Park Avenue-Redesign-Gensler-Architecture-NYCRendering for updated 399 Park Avenue by Gensler

399 Park Avenue, also known as the Citigroup Building, was sold in 2002 for $1.06 billion. Citigroup was one of the first to move uptown in the mid-20th century and its move back downtown had put Park Avenue landlords “on edge,” as reported by the Wall Street Journal. In 2002, it was the most expensive price paid for an office building in America. Earlier this year, major upgrades were announced for 399 Park Avenue including an outdoor elevated green space, a facade reclad from limestone to metal, and street level improvements. The redesign is being handled by the architecture firm, Gensler.