The double towers comprise 1.69 million square feet of mixed-use program and anchor the northwest corner of Brookfield Properties’ development proposal for the Hudson Railyards. As if carved from a solid mass, the towers emerge like stalagmites from a common base and gesture toward the site’s most significant features: the park to the south, the Hudson River to the west and the snaking High Line to both orientations. The base forms a street wall at the urban perimeter and is undercut and perforated for light, access and interface with the 6-acre park above. A Children’s Museum and a primary school intertwine programmatically within the base, sharing a large auditorium with views to the river, a green roof above the base, and a spiraling programmable stair. The stair bridges the park at one end and touches down at Hudson River Park at the other. The towers are bound at an upper story by a running track in the sky. This quarter-mile track with stacked running and walking levels is part of a fitness center that straddles the towers acting as a structural brace. A pool is extruded to the west. All common surfaces of the towers at the urban perimeter have a shear outer skin integrated with a structural web; the private inner surfaces are lined with floor-to-ceiling operable glass walls and exterior wood shutters that screen south and west exposures from solar gain while taking advantage of river views and breezes.