On New York’s Upper West Side, architects Jane Siris and Peter Coombs combined two penthouse apartments into a single residence. Above: “There were three very tall slit windows,” Siris says of the master bedroom, which overlooks the Hudson River, “so we made one big window.” (February 2009) Photo Credits » Bruce Buck, Barry Halkin, Kim Sargent, Peter Aaron/Esto, Durston Saylor, Marina Faust, Billy Cunningham, Durston Saylor, C. Z. Chai and Bao Shi Wang, Dominique Vorillon, Durston Saylor, Durston Saylor, Durston Saylor, Mary E. Nichols