Iraq, is a country in West Asia. It is bordered by Saudi Arabia to the south, Turkey to the north, Iran to the east, the Persian Gulf and Kuwait to the southeast, Jordan to the southwest, and Syria to the west. The country covers an area of 438,317 square kilometers (169,235 sq mi) and has a population of over 46 million, making it the 58th largest country by area and the 31st most populous in the world. Baghdad, home to over 8 million people, is the capital city and the largest in the country. Starting in the 6th millennium BC, the fertile plains between Iraq’s Tigris and Euphrates rivers, referred to as Mesopotamia, fostered the rise of early cities, civilizations, and empires including Sumer, Akkad, and Assyria. Known as the cradle of civilization, Mesopotamia saw the invention of writing systems, mathematics, navigation, timekeeping, a calendar, astrology, the wheel, the sailboat, and a law code.