610 Park Avenue, originally built as the Mayfair Regent Hotel in 1925 by architect J.E.R. Carpenter, was converted to a condominium in 1997. With just 68 residences across 15 floors, this elegant building retains its old-world charm and boutique feel, reminiscent of a small European hotel. Many units feature 2-3 bedrooms, and some include fireplaces. The building attracts an international clientele, adding to its cosmopolitan atmosphere.