North Africa and the Middle East: Physical Geography and Historical Crossroads

North Africa and the Middle East span some of the driest land on Earth. The Sahara, the world's largest hot desert, stretches across nearly all of North Africa, while the Arabian Peninsula holds the Rub al Khali, or "Empty Quarter," one of the largest continuous sand deserts anywhere. Yet within this dry region lies the Fertile Crescent, an arc of fertile land curving from the Persian Gulf through the Tigris and Euphrates river valleys (Mesopotamia) up through the eastern Mediterranean coast (the Levant) and down the Nile River valley in Egypt -- and it is here that some of the very first cities, writing systems, and organized agriculture in human history developed, earning the region its title as the cradle of civilization.

The Nile, the longest river on Earth, made ancient Egyptian civilization possible: its predictable annual flooding deposited fertile silt across otherwise desert land, supporting farming and population growth along a narrow ribbon of green through the desert. Sitting at the junction of Africa, Asia, and Europe, the region has been a historical crossroads for millennia, home in succession to Sumerian city-states, ancient Egypt, the Persian Empire, Greek and Roman rule, the Byzantine Empire, and later a series of Islamic caliphates -- each drawn by the region's fertile river valleys and its position astride major trade routes.