A barrel vault is an architectural structure formed by extending a simple arch along a length. This design creates a continuous, semi-cylindrical ceiling or roof, resembling a barrel cut in half. Barrel vaults are often used in large spaces, such as cathedrals and tunnels, to provide strength and stability. The construction of a barrel vault allows for the distribution of weight along its curved surface, making it an efficient choice for spanning wide areas. This technique has been utilized since ancient times, notably in Roman architecture, and continues to influence modern building designs.