1 North America 2 Meso America 3 Latin America 4 Middle East 5 Central Asia 6 East Asia 7 South Asia 8 Southeast Asia 9 East Africa 10 North Africa 11 West Africa 12 Central Africa 13 Southern Africa 14 Mediterranean Sea 15 Tigris and Euphrates River 16 Indus River 17 Sahara Desert 18 Europe 19 Ural Mountains 20 Himalayan Mountains 21 Mongolian Steppe 22 Nile River 23 Caribbean