The Indus Valley Civilization was an ancient civilization located in what is Pakistan and northwest India today, on the fertile flood plain of the Indus River and its vicinity. Evidence of religious practices in this area date back approximately to 5500 BCE. Farming settlements began around 4000 BCE and around 3000 BCE there appeared the first signs of urbanization. By 2600 BCE, dozens of towns and cities had been established, and between 2500 and 2000 BCE the Indus Valley Civilization was at its peak. Two cities, in particular, have been excavated at the sites of Mohenjo-Daro on the lower Indus, and at Harappa, further upstream. By 1800 BCE, the Indus Valley Civilization saw the beginning of their decline: Writing started to disappear, standardized weights and measures used for trade and taxation purposes fell out of use, the connection with the Near East was interrupted, and some cities were gradually abandoned.
The reasons for this decline are not entirely clear, but it is believed that the drying up of the Saraswati River, a process which had begun around 1900 BCE, was the main cause.Pakistan has the traces of the oldest civilizations of the world and from Mehargarh to Harrapa & Moenjodaro, Gandhara & Buddhist, Islamic & Mughal Era to British Raj, all periods have imprints in this region. The Indus valley civilization has still shrouded in mystery as their language has not yet been deciphered.