Asia is the largest continent, representing 29.13% of the Earth's surface. It has over 4 billion inhabitants spread across 47 countries. The terrain of Asia is characterized by vast plains like the Siberian and Indian Plains. It also contains major plateaus such as the Tibetan and Iranian Plateaus, as well as the highest mountains in the world like the Himalayas. Major seas include the Sea of Japan, South China Sea, and Red Sea. Notable lakes are Lake Baikal and the Caspian Sea, and significant rivers include the Yangtze, Ganges, and Indus.