Baghdad is the capital and largest city of Iraq. Situated on the Tigris, it is part of the Baghdad Governorate and is located near the Diyala River. With a population variously estimated at 6 or over 7 million, Baghdad forms 22% of Iraq's total population. In comparison to its large population, the city has a small area at just 673 square kilometers (260 sq mi). It is the second-largest city in the Arab world after Cairo, and the second-largest city in West Asia after Tehran. Baghdad is historically known as a global cultural hub.