Qubbat al-Khazna

The dome is most commonly thought to have been built under orders from the Abbasid governor of Damascus, Fadl ibn Salih in the late 8th century.^[4][5][6][7] This is based on the writings of later medieval Arabic writers, including Ibn Asakir, Al-Dhahabi, Ibn Kathir, and Ibn Taghrbirdi, though at least one historical Arabic writer, al-Badri (or Abu al-Tuqa), claimed that it was created in the reign of the earlier Umayyad caliph al-Walid (r. 705–715), who built the mosque. Depending on the source, the exact date of this construction varies and may have occurred under the Abbasid caliphs al-Mansur (r. 754–775), al-Mahdi (r. 775–785), or Harun al-Rashid (r. 786–809).^{[6]: 109–110} Modern writer Ross Burns cites the year of construction as 789.^[5] Alain George argues that the structure may part of an earlier Christian-era structure that was subsequently appropriated and modified during the early Islamic period.^[6]

The structure stands in the northwest corner of the mosque's courtyard. It is an octagonal chamber supported above the ground on eight columns.^[6]: 109 The Roman columns that were re-used for the structure's pillars were truncated to achieve the desired height but preserve original Roman-era capitals.^[1]

The exterior walls of the structure were originally covered in colorful mosaic decoration which imitated the earlier Umayyad-era mosaics in the rest of the mosque, although they are of slightly lesser quality than the latter.^[8][1] The mosaics were restored in 13th or 14th century and then in the late 20th century they were almost entirely redone based on existing fragments.^[1][2]

The dome used to hold the mosque's large endowments.^[9] Some Greek, Latin, Syriac, Coptic, Hebrew, Aramaic, and Georgian old manuscripts were also housed in Qubbat al-Khazna in the past (e.g. Uncial 0126, 0144, 0145).^[10][11] The manuscripts were generally kept out of view, but were allowed to be handled briefly by German scholars when German Emperor Wilhelm II visited Damascus in 1898.^[9]