Occupying the 18th floor of an Art Deco building in a Landmark district, this 2500 SF terrace wraps the four sides of a penthouse apartment, extending and nearly doubling its living space. The terrace design exploits the tension between distinct yet overlapping modes of physical and visual experience, bringing domestic program outside into distinct ‘rooms,' creating a layered middle ground, engaging and framing city and river beyond. With a material palette of steel, reclaimed teak, and natural and artificial stone, the terrace creates an integrated environment that bridges between the domestic scale of the single-story penthouse and the massive, building-scale presence of the parapet elements built to be seen from 18 stories below.The project embraces the technical challenges of rooftop construction, integrating them into a systemic design language: inventing a floating ground plane hat acts as ballast to support the cantilevered stainless steel railing, achieving stability without anchoring to building surfaces. The railings are integral garden elements, supporting an array of planter types and lighting, backed by surfaces which give depth to the parapet edge.