Adiabene was an ancient kingdom in northern Mesopotamia, corresponding to the northwestern part of ancient Assyria. The size of the kingdom varied over time; initially encompassing an area between the Zab Rivers, it eventually gained control of Nineveh and starting at least with the rule of Monobazos I, Gordyene became an Adiabenian dependency. It reached its zenith under Izates II, who was granted the district of Nisibis by the Parthian king Artabanus II as a reward for helping him regain his throne. Adiabene's eastern borders stopped at the Zagros Mountains, adjacent to the region of Media. Arbela served as the capital of Adiabene.