The document summarizes the early civilizations of ancient India, including the Indus Valley Civilization along the Indus River from around 2300-1700 BC and the later invasion of Indo-Aryan peoples from Central Asia after 1700 BC. The Indus Valley Civilization developed advanced urban planning in large cities like Harappa and Mohenjo Daro with sophisticated infrastructure, and it had India's first writing system. After this civilization declined, Central Asian groups like the Aryans began migrating in and imposed their language and religious traditions recorded in the sacred texts known as the Vedas, changing the region's culture and civilization.