Tehran is the capital of which country?

Tehran is the capital of Iran and the largest city in Tehran Province. With a population of around 9 million in the city and around 16 million in the larger metropolitan area of Greater Tehran, Tehran is the most populous city in Iran and Western Asia, and has the second-largest metropolitan area in the Middle East, after Cairo. It is ranked 24th in the world by metropolitan area population.

Tehran was first chosen as the capital of Iran by Agha Mohammad Khan of the Qajar dynasty in 1786, because of its proximity to Iran's territories in the Caucasus, then separated from Iran in the Russo-Iranian Wars, to avoid the vying factions of the previously ruling Iranian dynasties. The capital has been moved several times throughout history, however, and Tehran became the 32nd capital of Persia. Large-scale construction works began in the 1920s, and Tehran became a destination for mass migrations from all over Iran since the 20th century.