The Indus Valley Civilization also called the Sindhu Valley civilization is the largest of the 4 ancient urbanized civilizations, with other 3 being China , Egypt and Sumeria. The common feature of these civilizations is that, they were river-valley based. Indus Valley had its origins in Indus river valley. What was originally called Sindhu, is now referred to as Indus. Indus valley is now a part of present Pakistan , and extends over India , Afghanistan , Iran and even Saudi Arabia . The origins of Indus valley dates back to 5000 BC and continues up to 3200 BC.

When flourishing, Indus valley had nearly 1400 cities and towns. It had the largest trading centres, well connected by land and sea routes. Mystery pervades Indus Valley 's sudden fall and disintegration. Theories about the demise of this civilization centre-round, sudden floods, famine, deserts, foreign invasion, but all these fall short of any valid explanation of how this civilization disappeared.

By 1800 BC the nomadic Sanskrit speaking people appeared in the North western region. Referred to as Aryans, they were taken to be the mentors of Vedic religion, contained in their sacred religious texts called Vedas. Rigveda the most sacred text of Aryans mentions of God Indira of having destroyed Purs cities and towns and driving away the short, snub, and dark skinned people further south and east. Controversy surrounds whether the defeated were people belonging to Indus valley or not. But what is really unique about Indus valley people is their rich culture, for excavations at the various Indus sites proved amazing with finding of forts and walled towns, drainage system, variety burnt bricks, artifacts, seals, and writing samples.

Mahajanapadas towards Empires : From 1500 BC there seems to be the realization of thesis-antithesis-synthesis. The invading Aryans finally gave up their nomadic life, started establishing themselves in regions till then under earlier settlers. They took to agriculture and farming. Law and order was restored with village becoming the basic unit of administration. The Aryans were becoming Indianized by adapting the lifestyle of the locals. Their religion came to see certain changes; the simple practices came to be replaced by elaborate rituals, and acceptance of non-Aryan God Shiva as part of the religious pantheon.

The Mahajanapadas came into existence from 800 BC, the oldest being that of Kosala the

But, Magadha reached the pinnacle of power only under Mauryan rulers, like Chandragupta Maurya, Bindusara and Asoka. Mauryan rule left a great legacy that influenced the Indian traditions and values of governance and social norms of today. Asoka's dedication to Buddhism and his efforts at propagating it to other regions of India and world, in the form of Dhamma continues to be immortal. There can be no parallel testimony to Mauryan's rich contribution to Indian culture, with the Lion Capital of Sarnath piller being taken as the national emblem of independent India .

Much later, that is by 300 AD, the Guptas with official language Sanskrit revived the lost glory of Mauryas. During this period, Hindu religion received royal patronage and hence reached top heights of glory. After the Gupta rule came to an end, there emerged many small kingdoms, and feudal lords, providing the way for foreign invaders to make in-roads into India .

(The civilization of the Indus (circa 3300-1700 BC, Mature period 2600-1900 BC), shortened IVC was an ancient civilization that flourished in the Indus and Ghaggar-Hakra river valleys mainly in Sindh province of Pakistan and northwest and west of India, The extension to the west in Baluchistan. The stage of maturity of this civilization is technically known as the Harappan Civilization, after the first of its cities to be searched, Harappa. IVC excavation site has been ongoing since the 1920's.

Civilization is sometimes referred to as the Indus River Ghaggar-Hakra or civilization of the Indus-Sarasvati civilization. The name Indus-Sarasvati is based on the possibility of identifying the Ghaggar-Hakra river with the Sarasvati River mentioned in the Rig Veda, but this practice was challenged on grounds linguistic and geographical.)