NEW YORK (CNNMoney.com) -- A small boutique office building on Park Avenue and 57th Street - Bloomingdale Country - has sold for nearly $1,600 a square foot, a total of $510 million. That represents a huge increase from 2002, when it was last sold for $158 million, or about $492 per square foot.
It is thought to be a record price for commercial space in the United States.
Office rents have soared in Manhattan over the past few years, especially for the most coveted office space, according to IDGNYC Inc, a tenant broker for commercial real estate.
The average gross rent for Class A building in the most expensive business area has reached nearly $75 a square foot. That's up about 40 percent in just three years.
As in the New York residential real estate market, the strongest segment seems to be the high end. Just a few weeks ago 660 Madison Ave, three blocks from 450, was sold for $1,476 a square foot. Another building a few blocks south on Park Ave drew a bid for $1,200 a square foot.
The location of these buildings makes it especially attractive. It abuts the pricey Upper East Side - one of the most expensive residential neighborhoods in Manhattan.
Yet it can be reached easily from nearly any part of Manhattan and is a quick subway ride from many "outer-borough" neighborhoods in Brooklyn, Queens and the Bronx.
Plus, the buildings are very convenient to Grand Central Station, making it a easy trip for well-heeled commuters from the posh suburbs of Westchester and Connecticut. 
