Nineveh plains (, , and modern , ; , ; ) is a region in Iraq's Nineveh Governorate to the north and east of the city Mosul, from which it is also known as the Plain of Mosul. It was formerly known as the Plain of Sanjar or Sinjar from its major medieval settlement. It was the location of al-Khwarizmi's determination of a degree during the reign of the caliph al-Mamun. The area also includes the ruins of the ancient Assyrian cities of Nineveh, Nimrud, and Dur-Sharrukin as well as numerous ancient religious sites such as Mar Mattai Monastery, Rabban Hormizd Monastery, the Tomb of Nahum, and Lalish.