Iran, also called Persia, and officially the Islamic Republic of Iran, is a country in Western Asia. It is bordered to the northwest by Armenia and Azerbaijan, to the north by the Caspian Sea, to the northeast by Turkmenistan, to the east by Afghanistan, to the southeast by Pakistan, to the south by the Persian Gulf and the Gulf of Oman, and to the west by Turkey and Iraq. Iran covers an area of 1,648,195 km², with a population of 85 million. It is the second-largest country in the Middle East, the sixth-largest entirely in Asia, and its capital and largest city is Tehran.
Iran is home to one of the world's oldest civilizations, beginning with the formation of the Elamite kingdoms in the fourth millennium BC. It was first unified by the Iranian Medes in the seventh century BC, and reached its territorial height in the sixth century BC, when Cyrus the Great founded the Achaemenid Empire, which became one of the largest empires in history and has been decribed as the world's first superpower. The empire fell to Alexander the Great in the fourth century BC and was divided into several Hellenistic states.