Though they did not know it then, and though the first major excavations did not take place until the 1920s, these railway workers had happened upon the remnants of the Indus Valley Civilization, also known as the Harappan Civilization, after Harappa, the first of its sites to be excavated, in what was then the Punjab province of British India and is now in Pakistan. Initially, many archaeologists thought they had found ruins of the ancient Maurya Empire, a large empire which dominated ancient India between c. 322 and 185 BCE.
Before the excavation of these Harappan cities, scholars thought that Indian civilization had begun in the Ganges valley as Aryan immigrants from Persia and central Asia populated the region around 1250 BCE. The discovery of ancient Harappan cities unsettled that conception and moved the timeline back another 1500 years,situating the Indus Valley Civilization in an entirely different environmental context.
Mehrgarh in the foothills of a mountain pass in modern-day Balochistan in western Pakistan. There is evidence of settlement in this area as early as 7000 BCE.
The Indus Valley Civilization is often separated into three phases: the Early Harappan Phase from 3300 to 2600 BCE, the Mature Harappan Phase from 2600 to 1900 BCE, and the Late Harappan Phase from 1900 to 1300 BCE.
At its peak, the Indus Valley Civilization may have had a population of over five million people. The Indus cities are noted for their urban planning, a technical and political process concerned with the use of land and design of the urban environment. They are also noted for their baked brick houses, elaborate drainage systems, water supply systems, and clusters of large, nonresidential buildings.
The Indus Valley Civilization began to decline around 1800 BCE. Archaeological evidence indicates that trade with Mesopotamia, located largely in modern Iraq, seemed to have ended. The advanced drainage systems and baths of the great cities were built over or blocked. Writing began to disappear, and the standardized weights and measures used for trade and taxation fell out of use.
By 2600 BCE, small Early Harappan communities had developed into large urban centers. These cities include Harappa, Ganeriwala, and Mohenjo-daro in modern-day Pakistan and Dholavira, Kalibangan, Rakhigarhi, Rupar, and Lothal in modern-day India. In total, more than 1,052 cities and settlements have been found, mainly in the general region of the Indus River and its tributaries.
Mohenjo-daro is thought to have been built in the twenty-sixth century BCE; it became not only the largest city of the Indus Valley Civilization but one of the world’s earliest major urban centers. Located west of the Indus River in the Larkana District, Mohenjo-daro was one of the most sophisticated cities of the period, with advanced engineering and urban planning.
Archaeological remains at the lower town of Lothal. The bricks are uniform in size and are gray-brown colored. They are in a field of dead grass and are bordered by low-lying green trees and shrubs.
Harappa was a fortified city in modern-day Pakistan that is believed to have been home to as many as 23,500 residents living in sculpted houses with flat roofs made of red sand and clay. The city spread over 150 hectares—370 acres—and had fortified administrative and religious centers of the same type used in Mohenjo-daro.
Both cities had similar organization and featured citadels, central areas in a city that were heavily fortified—protected with defensive military structures. Additionally, both cities were situated along the Indus River. This structure would have allowed those at the higher levels of the buildings in either city to look down the river and see into the distance.
The remains of the Indus Valley Civilization cities indicate remarkable organization; there were well-ordered wastewater drainage and trash collection systems and possibly even public baths and granaries, which are storehouses for grain. Most city-dwellers were artisans and merchants grouped together in distinct neighborhoods. The quality of urban planning suggests efficient municipal governments that placed a high priority on hygiene or religious ritual.
Harappans demonstrated advanced architecture with dockyards, granaries, warehouses, brick platforms, and protective walls. These massive walls likely protected the Harappans from floods and may have deterred military conflicts. Unlike Mesopotamia and Ancient Egypt, the inhabitants of the Indus Valley Civilization did not build large, monumental structures. There is no conclusive evidence of palaces or temples—or even of kings, armies, or priests—and the largest structures may be granaries. The city of Mohenjo-daro contains the Great Bath, which may have been a large, public bathing and social area.
The people of the Indus River Valley Civilization achieved many notable advances in technology, including great accuracy in their systems and tools for measuring length and mass. Fire-baked bricks—which were uniform in size and moisture-resistant—were important in building baths and sewage structures and are evidence that Harappans were among the first to develop a system of standardized weights and measures. The consistency of brick size across cities also suggests unity across the various urban areas, which is evidence of a broader civilization.
Harappa, Mohenjo-daro, and the recently partially-excavated Rakhigarhi demonstrate the world’s first known urban sanitation systems. The ancient Indus systems of sewage and drainage developed and used in cities throughout the Indus region were far more advanced than any found in contemporary urban sites in the Middle East and even more efficient than those in many areas of Pakistan and India today. Individual homes drew water from wells, while wastewater was directed to covered drains on the main streets. Houses opened only to inner courtyards and smaller lanes, and even the smallest homes on the city outskirts were believed to have been connected to the system, further supporting the conclusion that cleanliness was a matter of great importance.
Harappans are known for seal carving— the cutting of patterns into the bottom face of a seal, a small, carved object used for stamping. They used these distinctive seals for the identification of property and to stamp clay on trade goods. Seals—decorated with animal figures, such as elephants, tigers, and water buffalos—have been one of the most commonly discovered artifacts in Indus Valley cities.
Seal from the Indus Valley civilization. Male figure in a cross-legged position, surrounded with animals and wearing a hat with two curved horns on either side.
The Indus River Valley Civilization is considered a Bronze Age society; inhabitants of the ancient Indus River Valley developed new techniques in metallurgy—the science of working with copper, bronze, lead, and tin. Harappans also performed intricate handicraft using products made of the semi-precious gemstone Carnelian.
Evidence shows Harappans participated in a vast maritime—sea—trade network extending from Central Asia to the Middle East. The civilization’s economy appears to have depended significantly on trade, which was facilitated by major advances in transport technology. The Harappan Civilization may have been the first to use wheeled transport, in the form of oxcarts that are identical to those seen throughout South Asia today. It also appears they built boats and watercraft—a claim supported by archaeological discoveries of a massive, dredged canal, and what is regarded as a docking facility at the coastal city of Lothal. Harappans also engaged in shell working, and shells used in their crafts have origins from as far away as the coast of modern-day Oman.
Trade focused on importing raw materials to be used in Harappan city workshops, including minerals from Iran and Afghanistan, lead and copper from other parts of India, jade from China, and cedar wood floated down rivers from the Himalayas and Kashmir. Other trade goods included terracotta pots, gold, silver, metals, beads, flints for making tools, seashells, pearls, and colored gemstones, such as lapis lazuli and turquoise.
We know about the maritime trade network operating between the Harappan and Mesopotamian civilizations is the discovery of Harappan seals and jewelry at archaeological sites in regions of Mesopotamia, which includes most of modern-day Iraq, Kuwait, and parts of Syria. Long-distance sea trade over bodies of water—such as the Arabian Sea, Red Sea and the Persian Gulf—may have become feasible with the development of plank watercraft that were each equipped with a single central mast supporting a sail of woven rushes or cloth.
Historians have also made inferences about networks of exchange based on similarities between artifacts across civilizations. Between 4300 and 3200 BCE—part of the Chalcolithic period, also known as the Copper Age—ceramics from the Indus Valley Civilization area show similarities with southern Turkmenistan and northern Iran. During the Early Harappan period—about 3200 to 2600 BCE—there are cultural similarities in pottery, seals, figurines, and ornaments that document caravan trade with Central Asia and the Iranian plateau.