Iran, also known as Persia and officially the Islamic Republic of Iran (IRI), is a country in West Asia. It is bordered by Iraq to the west and Turkey to the northwest, Azerbaijan, Armenia, the Caspian Sea and Turkmenistan to the north, Afghanistan to the east, Pakistan to the southeast, the Gulf of Oman & the Persian Gulf to the south. With almost 90 million people in an area of 1.648 million square kilometres, Iran ranks 17th in the world in both geographic size and population. The country is divided into five regions with 31 provinces. The nation's capital and most populous city is Tehran, with around 16 million people in its metropolitan area, other major urban centres include Mashhad, Isfahan, Karaj, and Shiraz.