Geography played a critical role in the early history of India, as it did in most locations around the world. Some key geographical factors played a role in the development of civilization and cities. First, the availability of rivers allowed farming settlements to grow into large urban areas. The Saraswati, Indus and Ganges Rivers were important water sources for irrigation. The flooding of the rivers left behind fertile soil for cultivation. Rivers were also used for transportation which allowed trade. The seasonal monsoons also brought plenty of water for the fields.
Another advantage of the geography for early Indian settlements is that it isolated India from potential invaders. Mountains and deserts formed a natural geographical advantage and separated the people of India from other areas including the Middle East and China. These barriers assured the city-states that they were safe and allowed civilization to develop without excessive military expenditures for defense. The city-states used these resources instead to develop water systems and paved streets.