Don't have a coronary, Mom—these guys are pros. At ESPN's annual XGames in and around Philadelphia (; August 15—19, all events free), the stairs, railings, and ramps outside City Hall and the First Union Center are the main arena for competing skateboarders, in-line skaters, and BMX bikers. After watching the action, take your adrenaline rush to the Philadelphia Zoo (3400 W. Girard Ave.; 215/243-1100), where you can go flying in a giant helium balloon. —Hillary Geronemus