Aby Rosen is a principal and co-founder of RFR Holding, a major New York City real estate investment and development company established in 1991. It has offices in New York, Stamford, Conn., and Frankfurt, Germany, where Rosen was born.

Rosen's childhood friend, Michael Fuchs, is the other main partner in the firm.

Rosen has acquired a vast portfolio of New York real estate holdings, including valuable skyscrapers like the Chrysler Building (405 Lexington Avenue) and the Seagram Building (375 Park Avenue). RFR projects have included the conversion of 530 Park Avenue and the development of the downtown condo One Jackson Square.

The firm has some 14 prominent properties in Manhattan and a few more in southwestern Connecticut.

Rosen is a prominent art collector. The Lever House art collection has included works by Jeff Koons, Damien Hirst and Tom Sachs. Rosen also owns dozens of Warhols. -TA