The History of India begins with the birth of the Indus Valley Civilization, more precisely known as Harappan Civilization. It flourished around 2,500 BC, in the western part of South Asia, what today is Pakistan and Western India. The Indus Valley was home to the largest of the four ancient urban civilizations of Egypt, Mesopotamia, India and China. Nothing was known about this civilization till 1920s when the Archaeological Department of India carried out excavations in the Indus valley wherein the ruins of the two old cities, viz. Mohenjodaro and Harappa were unearthed. The ruins of buildings and other things like household articles, weapons of war, gold and silver ornaments, seals, toys, pottery wares, etc., show that some four to five thousand years ago a highly developed Civilization flourished in this region. The Indus valley civilization was basically an urban civilization and the people lived in well-planned and well-built towns, which were also the centers for trade. The ruins of Mohenjodaro and Harappa show that these were magnificent merchant cities-well planned, scientifically laid, and well looked after. They had wide roads and a well-developed drainage system. The houses were made of baked bricks and had two or more storeys. The highly civilized Harappans knew the art of growing cereals, and wheat and barley constituted their staple food. They consumed vegetables and fruits and ate mutton, pork and eggs as well. Evidences also show that they wore cotton as well as woollen garments. By 1500 BC, the Harappan culture came to an end. Among various causes ascribed to the decay of Indus Valley Civilization are the recurrent floods and other natural causes like earthquake, etc.