Indus Valley Civilization, an ancient civilization on the Indian subcontinent that existed from about 2800 b.c. to 1700 b.c. The civilization is also called the Harappan culture and its people the Harappans after Harappa, one of the civilization's major cities. The Indus Valley civilization developed along the Indus River (in what is now Pakistan), but extended to the east in some areas (in what is now western India).
Little is known of the Harappans. Their only writings, which have not been deciphered, are short inscriptions on small stone seals (for stamping impressions) and amulets. The Harappans made bronze, copper, and stone tools. Their cities were built of brick and were all laid out in a distinctive gridiron pattern. Because of the degree of planning required for such cities, archeologists have concluded that the Harappans had a well-developed political system. The cause of the collapse of the Indus Valley civilization is unknown, but many historians speculate that it probably was destroyed by Aryan invaders.
The Indus Valley civilization was unknown until the 1920's. The earliest excavations took place at the two largest cities, Mohenjo-daro on the Indus River and Harappa on the Ravi River. Several hundred smaller settlements have also been discovered.