A walkway is a composite or umbrella term for all formal surfaces supporting walking. This inclues sidewalks, trails, paths, stairs, ramps and open paseos or passageways. The walkway is a path for walking that is generally not enclosed. It can be at ground level, or it can be elevated, such as a boardwalk, or a floating dock/trail. It can be a simple constructed path or something more complex to cross a road or a body of water. An open pedestrian overpass or a special tunnel is also an element of a walkway. It can also be used to board and remove passengers from aircraft to the terminal building.