A barrel vault is a continuous arching structure that can be semi-circular in shape, suggesting the roof of a tunnel, or pointed at the apex. It is often made by a sequence of side-by-side arches or vaults or by a continuous shell. The word is also used for any similar structure. Barrel vaults were popular in Europe from about A.D. 300 to 1000. They are found in many ancient churches built before the Gothic style came into use after 1100. They are also common in modern buildings that require heavy load-bearing capacity inside walls (such as banks and factories). The English word "vault" comes from the French word "volet" which means lid or cover. In architecture, the term "vaulted space" refers to an enclosed area above ground level. This could be a room or space within a building or a passage way leading to another area or floor. Vaulted spaces provide protection from the elements and visibility. They may also contain furniture or other amenities for users. Vaulted spaces come in two main types: open and closed-in. An open vaulted space has no supporting beams beneath its roof structure; instead, it uses joists or ribs to distribute weight across a large area. Closed-in spaces have transverse members below the roof surface called trusses or girders.