The muqarnas (Arabic: مقرنص; Persian: مقرنس) is a form of architectural ornamented vaulting, the "geometric subdivision of a squinch, or cupola, or corbel, into a large number of miniature squinches, producing a sort of cellular structure", sometimes also called "honeycomb" vaults from their resemblance to these. They are used for domes, and especially half-domes in entrances and apses, mostly in traditional Islamic and Persian architecture. When some elements project downwards, the style may be called mocárabe; these are reminiscent of stalactites, and may be called "stalactite vaults".
Muqarnas are typically applied to the undersides of domes, pendentives, cornices, squinches, arches and vaults. Muqarnas are concave-downwards shapes; a vertical line can be traced from the floor to any point on a muqarnas surface. They are also arranged in horizontal courses, as in a corbelled vault, with the horizontal joint surface having a different shape at each level. The edges of these surfaces can all be traced on a single plan view; architects can thus plan out muqarnas geometrically, as seen in the image. See these diagrams for clarity.
Basic principle of corbeled arch design
Corbelled vault carved into muqarnas (method of suspension for pendant points, one of which is missing, not clear).
Muqarnas do not have a significant structural role. The muqarnas need not be carved into the structural blocks of a corbelled vault; they can be hung from a structural roof as a purely decorative surface. Muqarnas may be made of brick, stone, stucco, or wood, and clad with tiles or plaster. The individual cells may be called alveoles.
Some modern muqarnas have been designed, if not built, with concave-up sections.