Iran (ēränˈ, ĭrănˈ), officially Islamic Republic of Iran, (2005 est. pop. 68,018,000), 1,648,000 sq km (636,290 sq mi) , SW Asia. The country's name was changed from Persia to Iran in 1935. Iran is bordered on the north by Armenia, Azerbaijan, Turkmenistan, and the Caspian Sea; on the east by Afghanistan and Pakistan; on the south by the Persian Gulf and the Gulf of Oman; and on the west by Turkey and Iraq. The Shatt al Arab forms part of the Iran-Iraq border. Tehran is the capital, largest city and the political, cultural, commercial, and industrial center of the nation.