What is the purpose of flying buttresses in architecture?

Flying buttresses are architectural elements primarily designed to support the roof structure of large buildings, especially in Gothic architecture. They consist of an arched structure that extends from the upper part of a wall to a pier or a buttress, which is set away from the wall. This design allows the walls to be thinner and taller while effectively distributing the weight and lateral forces away from the building.

The main function of flying buttresses is to counteract the lateral thrust produced by vaulted ceilings, enabling the construction of larger windows and thinner walls. This innovation not only allowed for the characteristic soaring heights of Gothic cathedrals but also resulted in increased illumination through stained glass and greater aesthetic appeal. While other options mention aspects like decoration, insulation, or mobility, they do not accurately reflect the structural role that flying buttresses play in architectural design. Hence, the correct answer focuses on their fundamental purpose of supporting the roof structure.