The Indus Valley or Harappan civilisation flourished around 2500 BCE with planned cities, drainage systems and standardised bricks. Mohenjo-daro stood on the Indus and Harappa on the Ravi; the Great Bath and granaries are its best known structures.
The Vedic period follows, giving us the four Vedas, with the Rigveda the oldest. Later came the rise of Buddhism and Jainism, founded by Gautama Buddha and Mahavira respectively, both reacting to ritual orthodoxy.
The Mauryan empire, founded by Chandragupta Maurya with Chanakya as adviser, peaked under Ashoka, who spread Buddhism after the Kalinga war. The Gupta period that followed is called the golden age for its achievements in mathematics, astronomy and literature.