architectural element formed by the extrusion of a single curve
A barrel vault, also known as a tunnel vault or a wagon vault, is a type of ceiling. It is an architectural element formed by the extension of a simple arch. It forms the shape of a semicircle over parallel walls.
- Fred Kleiner, Gardner's Art through the Ages: The Western Perspective, Volume 1 (Australia; United States: Wadsworth/Cengage Learning, 2010), p. 161