RFR Holding LLC is a Manhattan-based investment, development and management company founded in 1991 by principals Aby Rosen and Michael Fuchs, two childhood friends. RFR Group oversees about $10 billion of real estate worldwide, including in Rosen and Fuchs' native Germany (RFR Holding GmbH). After starting out by buying distressed assets from sellers such as the Resolution Trust Corp., which were liquidating troubled lenders' assets, the firm owns now iconic Manhattan properties including the Seagram Building (375 Park Avenue) and Lever House (390 Park Avenue).

Rosen seems to crave the limelight, while Fuchs tends to shun it. The firm has had several very public disputes with investor Harry Lis and developer Ian Schrager, who worked with them on the Gramercy Park Hotel project.

Rosen is a passionate art collector, once telling an interviewer that about 10 percent of his investments are in art (the same proportion as in very conservative paper; the other 80 percent is in his company). The firm says it seeks to use art and architecture to create uplifting and inspiring environments; its buildings have displayed works by artists including Pablo Picasso, Andy Warhol and Damien Hirst.