The Indus Valley civilization flourished around 4500 years ago along the Indus River valley in what is now Pakistan and parts of northwest India. Major sites included Mohenjo Daro and Harappa, which had sophisticated infrastructure like streets laid out in grids and advanced drainage systems. The civilization engaged in agriculture of crops like barley, wheat, and sesame and had craft specializations like metalworking. However, around 2000 BCE, the civilization began to decline possibly due to climate change or flooding, and its infrastructure and cities were abandoned, causing the civilization to vanish.