This 8 room penthouse, atop a venerable pre-war Park Avenue building, has been reconfigured so that the public spaces are contained within a glass box, transparent to the northern and southern exposures, while maintaining seclusion in the private spaces. A skylight and subtly curved wall draw circulation from the entry to a large loftlike space where lift and slide glass doors connect to and incorporate the terrace. New sycamore partitions and millwork define the spaces at the limits of the building envelope. Moving pocket walls provide the ability for free flowing spaces or discrete enclosures at will.