The Indus civilization was one of the ancient civilizations that was located in today's time which is northwest India and Pakistan. It was on the fertile flood plain of the Indus River and its vicinity. The name "Indus civilization" was derived from the main river of that region "Indus".
There were two particular cities that are well known at the time of Indus civilization. Mohenjo- Daro and Harappa. Mohenjo- Daro was located on the lower Indus and Harappa at the further upstream. Indus civilization sometimes is also known as Harappan civilization. This civilization lasted from about 3000- 2500 BC to about 1500 BC. These two cities had a population of about 35000 each. "These cities were far more advanced than their counterparts in prehistoric Egypt, Mesopotamia or anywhere else in Western Asia." (Ancient Indian history: The Indus Valley civilization (2500 BC – 1500 BC)). Harappan cities seemed to have almost the same structure as the cities of Mesopotamia and Egypt. Along with Mohenjo- Daro and Harappa there were several other small cities and villages spread out according to a meticulously planned grid. There were also temples, public buildings, markets etc. and these were all located in convenient locations. In these cities they had large streets that were paved with bricks and were remarkably straight. In fact drains and gutters were designed in such a manner that it might have been considered as the most elaborate urban sewer system of ancient times. (Book page 65) Dozens of cities and towns started to build up and between 2500 and 2000 BCE the Indus Valley Civilization was at its peak. .
By 1500 BCE (till today there is considerable disagreement about this date) the Aryans migrated into the Indian subcontinent from central Asia. This was a large group of nomadic cattle herders crossing the Hindu Kush Mountains and came in contact with Indus Valley Civilization.