1·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.
最独特的特点是圆屋顶，要让圆屋顶安置于方形基础上，可利用两种方式：内角拱(方形基础每个角落的拱门变为八角形)或穹隅。