A minimum of thirty percent of the gross acreage within the town center district shall be reserved for and used as open space. For the purpose of the town center zone, open space shall be defined as all of the land in the town center zone site not devoted to building, parking structures, paved streets and parking area improvements, but including such areas as landscaped medians, pedestrian ways, courtyards, and other landscaped exterior space, whether public or private. (Prior code § 5-2-4(P)(4)(c))