India is located in Asia, isolated by natural barriers such as the Himalayas mountains and deserts. Two early civilizations developed in India - the Indus River Valley civilization and along the Ganges River Valley, supported by monsoon winds. The Harappans were farmers and traders who built well-planned cities with structures like the Great Bath, and they engaged in trade along the route between China and Mediterranean regions. Major achievements of ancient Indians included the development of the decimal number system including zero, scientific discoveries like the Earth being round and orbiting the sun, and advances in medicine such as inoculation.