Aššur, also known as Ashur and Qal'at Sherqat, was the capital of the Middle Assyrian Empire for a time, of the Neo-Assyrian Empire and a semi-independent state during the Parthian Empire between the 2nd century BC and mid 3rd century AD. The remains of the city lie on the western bank of the Tigris River, north of the confluence with its tributary, the Little Zab, in what is now Iraq, more precisely in the al-Shirqat District of the Saladin Governorate. Assur lies 65 kilometres (40 mi) south of the site of Kalhu and 100 km (60 mi) south of Nineveh.