The honeycomb ceilings of Islamic architecture solve the problem of putting a dome on a square room.
Muqarnas are tiers of tiny niches stacked and projecting over one another, like a honeycomb or stalactites. Built from a small set of simple shapes combined by strict geometric rules, they bridge the awkward zone between a square room and a round dome. One dome in the Alhambra has at least 5,000 cells.
Put a round dome on a square room and you have a problem at the corners. One old solution was the squinch, an arch or niche across each corner. Muqarnas grew out of the squinch into something far more elaborate: rows of small niche-like cells, each projecting over the row below like a corbel, filling the transition zone with a cascade of faceted surfaces. In Europe they have been called honeycombs or stalactites.
The system is remarkably economical. Each composition uses a limited set of simple prismatic shapes, combined according to precise rules around a few axes of symmetry, yet the results can be endlessly varied. Materials change by region: carved stone in Syria, Egypt and Turkey; plaster or wood in North Africa; brick, sometimes faced with plaster or tile, in Iran and Iraq. Some plaster versions actually hang from a hidden structure above.
Where it began is debated. The earliest surviving examples date from the 11th century, appearing almost simultaneously from Iraq and Iran to Egypt and North Africa. Some scholars think it developed in north-eastern Iran; others argue for Abbasid Baghdad, whose influence could explain its rapid spread. The oldest complete muqarnas dome to survive into modern times was the Imam Dur Mausoleum at Samarra, finished in 1090. In 1427 the mathematician al-Kashi wrote the oldest surviving treatise on muqarnas.
The form travelled widely. It reached its peak of sophistication in the Alhambra in Granada, where the 14th-century dome of the Hall of the Two Sisters unfolds from a central summit in at least 5,000 cells. It even crossed religious lines: the Cappella Palatina in Palermo, a Christian church of about 1140, has the world's largest rectangular muqarnas vault, in carved and painted wood. The art historian Oleg Grabar suggested the Alhambra domes represent the rotating heavens.
Source: Wikipedia — Muqarnas · Text summarised from Wikipedia (CC BY-SA 4.0)
