MqrnS (Persian: mqrns), also known as Ahoopay (Persian: ahwpy) in Iranian architecture and Mocarabe in Iberian architecture, is a type of ornate vaulting in Islamic architecture. It is the quintessential form of Islamic architecture, and it is an essential part of the vernacular of Islamic structures. The word muqarna means "to bend or bow" in Arabic, but it can also be translated as "to curve" or "to wind." In structural terms, muqarnas are ribbed dome shapes whose ribs radiate out from the center of the structure like the petals of a flower. Muqarnas were invented in Persia (now Iran) by Abu Ali Ibn Abdallah al-Shafih, who was born around 770 AD. The first documented use of this type of vault was over a mosque that he built in Isfahan for the Abbasid Caliphate. Although there are variations between examples, all generally follow the same basic plan. The roof is made up of several layers. The lowest layer is called the plating because it covers the entire floor. It is usually made of wood but sometimes of metal. Next comes the springing, which is either stone or brick. Above that is placed the crowning, which is often but not always flat, made of clay or terracotta. At its highest point, the crowning reaches the length of the room beneath it.