Classical Adiabene, Syriac Ḥadyāb, refers to the region between the Upper and Lower Zab rivers, from the Tigris in the west to Mt. Ṣalāḥ al-dīn (= Mt. Pirmum) in the east. Its main city was the ancient Assyrian Arbaʾil (modern Arbīl), seat of Ishtar of Arbela, goddess of war and collaborator in the creation of humans. Ḥazzā, the name referring to Adiabene in Arabic sources, was an earlier center of the region, located some 12 km. southeast of Arbīl. The impressive citadel of Arbela contains remains from the Neolithic period to modern times, including Sasanian, Christian, and Islamic levels in between. Arbaʾil was a caravan city on a trade route linking southern Mesopotamia and Persia with Palestine and Egypt, as shown in an Aramaic letter signed by Arshama, the Achaemenid satrap of Egypt (late 5th cent. BC). During the 1st cent. AD the local royal family converted to Judaism, under Izates, who enjoyed quite a remarkable reign according to Josephus (‘Antiquities’, 20.17–94). Christianity spread into this region quite quickly, with Papa possibly serving as its first metropolitan as of 310. The Synod of 410 held in Seleucia-Ctesiphon declared Adiabene a metropolitan seat, occupied in that year by Daniel. Thereafter, Adiabene grew into a great administrative province of the Ch. of E., though it suffered several persecutions, especially under Shapur  II (309–379). The jurisdiction of the metropolitan of Adiabene was not restricted to his own province but extended at one point to include Azerbaijan and Nineveh, divided into nine suffragan dioceses. When Mosul grew in political and economic importance at the beginning of the 9th cent., it separated from Adiabene, but the latter continued to be a Metropolitan see until the beginning of the 17th cent. By the end of the 18th cent. most of Adiabene joined the Catholic uniate movement, and Arbela fell under the jurisdiction of the Chaldean archbishop of Kirkuk.