Tehran is the capital and largest city of Iran. In addition to serving as the capital of Tehran province, the city is the administrative center for Tehran County and its Central District. With a population of around 9.4 million in the city as of 2018, and 16.8 million in the metropolitan area, Tehran is the most populous city in Iran and Western Asia, the second-largest metropolitan area in the Middle East after Cairo, and the 24th most populous metropolitan area in the world.