The historic Observatory had been hindered by the lack of a cohesive planning strategy that would allow the building to function as an integrated whole. The enfilade system of circulation had encouraged students and faculty to circulate through classrooms while they were in use. The need for independent passages to other parts of the Observatory had transformed the once graceful, historic rooms. A linear circulation spine became the organizing device around which the historic rooms would be liberated and accessed. A series of new labs and classrooms would also be accessed from this public spine, thus connecting the historic Observatory with the state of the art 21st century facility. The new circulation spine, naturally lit by an east-facing clerestory, also functions as a ‘gallery’ for the display of objects that contribute to the legacy of the facility. This active central artery is at once a social space for interaction among students, faculty and visiting scholars and a framed portal through which the Arboretum is experienced.