Muqarnas is an ornamental decoration typical of Islamic architecture, mostly found in the vaults of buildings. Also known as the alveoli or stalactite decoration, they were also used in the domes, niches and doorways. They became more widespread from the 12th century onwards and could be made of a variety of materials such as stone, stucco, pottery and brick. In Sicily, they are found in many Norman buildings such as the Palatine Chapel and the Zisa.