Mosul is a major city and the capital of Nineveh Governorate, located in northern Iraq on the west bank of the Tigris River opposite the ancient Assyrian city of Nineveh. The history of the region dates back to the Assyrian period in the first millennium BC, when Mosul was founded in the seventh century BC, then it became part of the Seleucid Empire after the arrival of Alexander the Great in 332 BC. The Muslim Arabs entered the city under the leadership of Rab’i ibn al-Afkal al-Anazi in 637 AD after the victory of the Muslims over the Sassanians in the Battle of Al-Qadisiya. During the 12th century AD, Mosul reached the peak of its prosperity when it was ruled by the Zengid dynasty. The oldest and most important layer of the architecture of the old city of Mosul dates back to the 12th and 13th centuries AD, which reflects the importance of the great city, its strength, and its influence during the era of the Zengids.