vances were made in all crafts. Similarities in pottery, seals, figurines, ornaments etc. document intensive caravan trade with Central Asia and the Iranian plateau. There were already towns with walls and a grid pattern of streets, such as Rahman Dheri. Terracotta models of bullock carts attest to improved transport in the Indus Valley. This led to considerable cultural uniformity over a wide area.
A relatively short but still poorly known transition phase, between 2700–2500 BCE, turned the Early Harappan culture into the Mature Indus Civilization. During this phase the Indus script came into being. The size of the burned brick, already standardized during the Early Harappan period, was fixed in the ratio 1: 2: 4 most effective for bond- ing. Weights of carefully cut and polished chert cubes form a combined binary and decimal system.5) The society became so highly organized that it was able to complete enormous projects, like building the city of Mohenjo-daro around 2500 BCE.
The acropolis of Mohenjo-daro, a cultural and administrative centre, has as its foundation a 12 metre high artificial platform of 20 hectares. Just the platform is estimated to have required 400 days of 10,000 labourers. The lower city of at least 80 hectares had streets oriented according to the cardinal directions and provided with a network of covered drains. Many of the usually two-storied houses were spacious and protected from the dust and crowd of the streets and had bath- rooms and wells. The water-engineering of Mohenjo-daro is unparallelled in the ancient world: the city is estimated to have had some 700 wells constructed with tapering bricks so strong that they have not collapsed in 5000 years. The Great Bath was made watertight with bitumen and a high corbelled outlet made it possible to empty it easily. The massive city walls are supposed to be mainly defenses against flood water.
The absence of palaces and temples — which may well be illusory6) —
The ratios are 1/16, 1/8, 1/6, 1/4, 1/2, 1 (= 13 g), 2, 4, 8, 16, . . . 800.
Massimo Vidale (in press b) suggests the presence of a palace complex that
consists of “houses” (including a private bath resembling the Great Bath) in the HR area of Mohenjo-daro.
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