Which architectural element provides structural support above an arch?

The keystone is the central stone at the summit of an arch, and it plays a crucial role in providing structural support. When an arch is constructed, the keystone is the last stone placed, and it locks the other stones (called voussoirs) into position. This locking mechanism allows the weight from above to be distributed evenly throughout the arch. As forces exert downward on the arch, the keystone resists those forces and maintains its stability, preventing the arch from collapsing.

In contrast, while spandrels, springing stones, and piers contribute to the overall structure and design of an arch or archway, they serve different purposes. Spandrels are the triangular sections located between the curve of the arch and the vertical supports, providing a visual transition but not directly supporting the arch itself. Springing stones are the stones at the base of the arch that help to initiate the arch shape, but their primary role is to allow the arch to rise from its support rather than to act as the primary support mechanism. Piers are vertical supports that hold up the entire structure but do not have the same specific function as the keystone in the context of an arch.

Overall, the keystone is essential for the integrity of the arch