India is located on the Asian subcontinent, which is separated from the rest of Asia by the Himalayan mountains. The Indus River, which flows from the Himalayas, was important for the development of early agriculture and cities in the Indus River Valley civilization like Harappa and Mohenjo Daro. While this Harappan civilization developed advanced urban planning and trade, the reasons for its decline are unknown. Nomadic Aryan groups later invaded and their Sanskrit language became dominant, providing historical texts about their society that practiced herding and early forms of government under local rulers.