 Muqarnas are elaborately carved ceilings to semidomes , often used in mosques . They are typically made of stucco ( and thus do not have a structural function ) , but can also be of wood , brick , and stone . They are characteristic of Islamic architecture of the Middle Ages from Spain and Morocco in the west to Persia in the east . Architecturally they form multiple tiers of squinches , diminishing in size as they rise . They are often elaborately decorated . 
