A groin vault is formed when two barrel vaults intersect at right angles. Vaults are ceilings built in the style of an arch and are often used in corridors or tunnels. Groin vaults are normally rounded in Romanesque fashion or pointed in Gothic fashion.
Groin vaults give the advantage of better weight distribution. The weight of the ceiling is concentrated in each corner of the "X" created by the intersection. When the corners are buttressed, the walls between the buttresses can be removed to allow for large windows or openings. Some medieval constructions made use of a six-part groin vault with six points of weight distribution, allowing for even greater flexibility with wall openings and window designs.