Flying buttresses are a type of architectural element that is commonly seen in medieval cathedral designs. Flying buttresses are formed by protruding from the walls of a structure down to the foundation in a half-arched shape, which was first established in Romanesque architecture and later refined in Gothic architecture. They provide additional support for heavy roof structures and allow larger windows than would otherwise be possible. The name "flying" comes from the appearance of these elements when viewed from below; they appear to be flying away from the wall. During the 11th century, architects began to use the term "flying buttress" to describe the supporting structure for a wall or roof that did not actually protrude out from the wall itself but rather ran along it inside the room it protected. The word "buttress" is derived from the French word "bourse", which means counterbalance. So a buttress is something that provides balance or counterweight. In early church design, the space above the nave was generally left open to allow for maximum light and air circulation within the building. As time went on, however, architects began to suggest that a ceiling might be useful for adding support to the nave roof or for providing decorative coverings. The first known attempt at forming an integral ceiling within a church occurred around 1030 in France where wooden beams with cross-sections ranging from simple triangles to more elaborate shapes such as X's and Y's were used to support the nave roof.