The son of Hârûn er Rashîd was the last of the great ’Abbasides and the same Mâmûn (808–833 A. D.) whose name is found in the Dome of the Rock, not only in the Ḳufic text over the arcade, but also on the four fine bronze gates of the outer octagonal wall, where it accompanies his true date, answering to 831 A. D. The beams of the roof above this wall bear a yet later date, answering to 913 A. D., and it seems probable that El Mâmûn built this wall, and that it did not form part of ’Abd el Melek’s original design. It certainly existed in 985 A. D., and is noticed by Ibn el Fâḳîḥ in 902 A. D., but El Y’aḳûbi says that ’Abd el Melek “built a dome over the Ṣakhrah and hung it round with curtains of brocade,” on the occasion when--according to the letter preserved by later writers--this khalîfah desired “to build a dome over the Holy Rock in order to shelter Moslems from the inclemency of the weather.”[477] The outer wall in question is adorned with fine windows, which were filled with coloured glass in 1528 A. D. It has a parapet with round arches, supported by coupled dwarf pillars, and with recesses under the arches, as was discovered in 1873. These, and the upper part of the wall outside, were covered with glass mosaics of which traces have been found; while the lower part, according to various accounts from the tenth to the twelfth century, was adorned as now with marble.[478] The arcade of the parapet was still visible in 1486 A. D., when Breidenbach made his sketch of the building; but the whole of the upper part of the wall and parapet was covered over later with the beautiful Kishâni tiles, which bear the date 1561 A. D. In its original condition the octagonal wall and the arcaded parapet resembled in style the Sassanian buildings at Ctesiphon and Takht-i-Bostân in Persia; and an exactly similar arcade with recessed panels, under round arches on coupled dwarf pillars, exists in the beautiful kiosque at ’Ammân in Gilead, which--in plan--is similar to the Persian buildings above mentioned. This kiosque is probably Moslem work, and an early mosque exists close by.[479] Thus while the original work of ’Abd el Melek shows the influence of Byzantine art, the additions made by the Baghdâd khalîfah El Mâmûn, in 831 A. D., very naturally show Persian style.