what is the center stone in an arch called
The central feature of an arch is the keystone, or the wedge-shaped stone at the very top of the arch. It is the last stone placed during construction, and it locks all the other stones of the arch into position. The keystone bears almost no weight, but is the center of redirecting the weight of the structure down and outwards. The Romans used arches with circular tops, called rounded arches, which were made of stone.