(Arabic: مقرنص). (Also known as stalactite or honeycomb vaulting). A form of decorative vaulting in Islamic architecture. In muqarnas, the surface of a vault or dome is subdivided into cells that have no load-bearing function. Web resource here and here. Video here.

Ali Akbar Isfahani. Muqarnas vault, entrance iwan, Royal Mosque, Isfahan, Iran. 17th c.