Iran has an area of 1,648,195 km2 (636,372 sq mi). It is bordered to the Armenia , Nakhchivan, Republic of Azerbaijan , Afghanistan, Pakistan Persian Gulf and the Gulf of Oman; Iraq and Turkey The most famous mountainous are the Caucasus, Zagros, and Alborz. And the only large plains are found along the coast of the Caspian Sea and at the northern end of the Persian Gulf. There are wide range of climates in different parts of the country; Hot desert, Cold desert , Hot semi-arid ,Cold semi-arid, Hot-summer Mediterranean and Continental Mediterranean climates. The majority of the population speaks Persian, which is also the official language of the country.