The arena of the Rock (Qubbet el-Sakhra) in Jerusalem is one of the greatest of Muslim memorials, still sometimes called the Mosque of Omar - incorrectly, because it is not a mosque and does not date from the time of Caliph Omar. It was constructed by Abd el-Malik (685-705), the fifth Omayyad Caliph: an octagonal construction with a high dome over the holy rock of Moriah. The imposing upshot of the Dome of the Rock results from the blend of fine proportions and extravagant beautification with an apparently simple ground-plan consisting of three concentric elements. Round the rock is a ring of wharfs and columns sustaining the dome; a wide ambulatory divides this ring from an octagon, also formed by piers and columns; and this in turn is estranged from the octagonal outer walls by a narrow ambulatory.