Mini’s newest marketing experiment is set to open from Sept. 4 till Sept. 13 atop a building in Clinton. During the day the space will act as a 4,500-square-foot landscaped park. An 8-foot grassy hill implanted with plastic dishes that serve as seats, and will hold activities like symposiums on green living and Pilates classes. At night, 320 flashing L.E.D.’s and a pulsating 28-foot lighting tower will turn the rooftop into a site for invitation-only parties and other events. Lounge areas, a sun deck, art and photo studios, and free wifi access will be available to all Rooftop guests.