To allow a dome to rest above a square base, either of two devices was used: the squinch (an arch in each of the corners of a square base that transforms it into an octagon) or the pendentive.
Pendentives make possible support of the dome on a square framework of four huge equal arches resting on huge piers.
穹隅尽可能地支撑着四个巨大的相等的拱形组成的正方形框架之上的圆屋顶，停留在巨大的墩上。
3
The advantages of two different structural types can be fully developed by combining the single-layer spherical dome and the double-layer square pyramid space grids into a new structural type.