The clients for this townhouse nearby the Museum of Natural History engaged ACHA to renovate their duplex apartment. The design includes the addition of a rooftop office. Working primarily through the section of the building, ACHA designed a sequence that begins with a spiral stair connecting the lower bedroom floor with the living room and kitchen. By restructuring the roof, ACHA was able to raise the ceiling of the of the living room with a skylight that visually connects the rooftop office with the living room. From the office, the sequence of spaces continues out to the roof terrace.