What structural problem does a squinch solve beneath a dome?

In Islamic architecture, a squinch serves as a structural transition device that solves the problem of supporting a circular or polygonal dome over a square or rectangular room.12

By filling in or bridging the upper corners of a square space, the squinch effectively transforms the room's layout into an octagonal opening, providing the necessary base to support the weight of the dome above. Architects achieve this through various methods, such as:12

• Building arches diagonally across the corners.1
• Constructing niches topped with a half-dome.12
• Using corbelled masonry courses that project outward.1
• Employing small conical vaults.1

In later Islamic traditions, these functional squinch forms were further developed into elaborate decorative elements known as muqarnas, or stalactite-like work, which evolved from the structural rearrangement of these corner units.12