By 2500 B.C. the Indus Civilization was a flourishing culture. It was centered around the River Indus and was much larger than its counterparts in Egypt and Sumer. The area claimed by the Indus Civilization was 1,100 miles ( 1,770 km ) from east to west and 800 miles ( 1,290 km ) from north to south.
Over one hundred sites have been recovered in the area with five being identified as cities. The most well knows of these are Mohenjo-Daro and Harappa. These cities were wonders. Each was built according to a carefully planned layout. The streets were laid out in a grid pattern and built so as to take advantage of the northerly winds for ventilation. The width of the streets allowed easy access of carts and beasts of burdens. The corners of buildings were rounded off at intersections so pedestrians would not be injured. Perhaps the most amazing engineering feat of this ancient civilization was their drainage system. Each house contained baths and toilets which were connected to a central drainage system.
Around 1700 B.C. the cities were abandoned suddenly. No definite answer can be given as to why this happened. Flooding is the most likely cause as people were forced to flee from their homes to escape the rising water levels of the river. Earthquakes and foreign raiders have also been suggested.