Iraq is located in Western Asia, at the northern end of the Persian Gulf. Its geography is defined by the Tigris and Euphrates rivers, which flow through the center of the country from the northwest to the southeast. The fertile land between these two rivers was known in antiquity as Mesopotamia, often called the 'Cradle of Civilization,' where writing, the wheel, and agriculture first developed. Baghdad is the capital and largest city, situated on the Tigris. Iraq's landscape varies from the mountainous Zagros region in the north to the Syrian Desert in the west and the marshlands in the south near the Persian Gulf. The country possesses some of the world's largest oil and natural gas reserves. Historically, it was the site of the ancient city of Babylon. The climate is mostly arid with mild to cool winters and very hot, dry summers.