Harappan Engineering

What impresses most about the Indus Civilisation, also known as Harappa Culture, is its  expanse of  more than a million sq km. The Harappa Culture dates back to circa 2600-1900 BCE. Its vast expanse, uniformity, accurate weights and measures system, elaborate hydraulics, metallurgy, pyrotechnology and agriculture are simply amazing. It is bewildering to note that the Harappan legacy is deep rooted and provides the substratum of the Indian Civilisation. However, the culture does not find a mention in our history or even legends says D P Agrawal.

What impresses most about the Indus Civilisation, also known as Harappa Culture, is its  expanse of  more than a million sq km. The Harappa Culture dates back to circa 2600-1900 BCE. Its vast expanse, uniformity, accurate weights and measures system, elaborate hydraulics, metallurgy, pyrotechnology and agriculture are simply amazing. It is bewildering to note that the Harappan legacy is deep rooted and provides the substratum of the Indian Civilisation. However, the culture does not find a mention in our history or even legends says D P Agrawal.

In this essay we will highlight some of the architectural-engineering achievements of the Harappans and also the all  pervasive legacy they bequeathed.


Two things are remarkable about the Harappans: One, their town planning; two, their overall plan of the cities in their geographical expanse. If their cities were laid out on a grand master plan, it would be the most remarkable thing of the third  millennium context. All the major cities are about 300 km apart and represent both cultural and economic entities. For example, Harappa controlled the trade of the hilly hinterland and in historical times gave rise to the Panjabi culture and language. Mohenjodaro controlled the overseas trade and it was the town where Sindhi culture and language originated.

Generally, Mohenjodaro was considered the model for Harappan town planning, with an acropolis to the west, separated from the lower town meant for the common people. But most Mature Harappan town plans were different from that of Mohenjodaro. For example, Allahdino, Amri, Banawali, Dholavira, Lothal, Rojdi, Surkotada, Ropar, Harappa and Hulas had their distinctive plans. Deep digging has revealed that Harappa had pre-Harappan beginnings. At Harappa, there is an acropolis to the west, but there is also an important part of the city to the north of the acropolis, called Mound F with the Granary and husking floors. In Dholavira, in Kachchh, the acropolis is near the middle of the enclosed settlement, and there are both Lower and Middle Towns. Only Kalibangan resembles Mohenjodaro in terms of its layout. In fact, of all the Mature Harappan sites there are only two – Mohenjodaro and Kalibangan – that resemble each other!

The selection of the site for Mohenjodaro may have been partly influenced by the convergence of riverine and land trade routes. Whatever the economic or religious compulsions, they had to find some concrete solution to the problem of floods. Mohenjodaro was, therefore, built on platforms to raise the buildings. The early platforms were foundation structures that substantially raised the city much above the flood levels. Possehl calculated that building platforms involved a massive amount of work: it must have taken approximately 4 million workdays! Organisation of such huge works in the third millennium is simply amazing.

The building of the platforms at Mohenjodaro makes it clear that they  had a plan for the entire city before they started building it up. Planning on this scale, especially planning that was accompanied by the will and means to bring it into reality, is something special for the third millennium BCE.

Some of the towns, like Kalibangan, show a distinct fortification. The roads had standard widths: while the narrowest (evidently a lane) path, was 1.8 m in width, the others were 3.6 m, 5.4 m and 7.2 m respectively.
Most of the buildings had an upper story. Some of the larger buildings could have had two, even three, additional floors below the roof.

Most remarkable was the method of laying out the floor during Harappan times at Kalibangan. Broken, hard-baked terracotta nodules, interspersed with charcoal, were first placed as the soling material. Over this was laid out a layer of clay. The local engineers explained, “…Even now this technique is used for providing a hard soling with intermixture of charcoal pieces in laying out the floors in areas where the soil is salty and the subsoil water-table is relatively high. The presence of charcoal serves two purposes. In the first place, it prevents the moisture from travelling up and thus saves the walls from the saline effects; otherwise they begin to crumble on account of saltpetre. Secondly, it acts against termites and thus gives relief to the occupants from them”.

At Banawali, in Haryana,  the Citadel fortification formed a semi-ellipse on plan. In the Lower Town the  streets ran in all directions. The most noteworthy feature of the Banawali fortifications was the provision of a moat.
Lothal, about 80 km south-east of Ahmedabad, has the world’s earliest dockyard. Oriented along the cardinal directions and forming a rough rectangle on plan, the fortified settlement measures about 225 m east-west and 280 m north-south.

Dholavira, in Kachchh, has not only yielded a unique town-plan but it has also brought to light a remarkable system of water-supply. The site also has yielded the only stadium known to belong to the Harappans.


For measuring large distances and structures, the Harappans had to have a developed technology of mensuration. For linear measures, two systems were in vogue: cubits and a long foot.  A cubit was about 52 cm (52.5 to 52.8 cm) and the long foot, 33.5 cm. Rao reports a shell object (now also reported from other sites in Saurashtra) with four slits, which was probably used to measure angles. A shell scale from Mohenjodaro and another of ivory from Lothal indicate the Harappan measures of length. The scale from Lothal has a length of 128 mm. The smallest divisions are 1.7 mm and the next unit is 33.46 mm.  This scale is divided decimally. On both the Mohenjodaro and Lothal scales, a bigger unit of 67.056 mm can also be discerned. Both foot (13.2 inch or 33.5 cm) and cubit (20.5 in or 52.5 cm) seem to be in vogue, as indicated by the measures of buildings and roads. For example, the main walls of the Harappan granaries measured 30 cubits and their widths 10 cubits; some houses in Lothal measured 40 x 20 units of the Harappan foot. Rao has also pointed out that the 17.7 mm Harappan division is very near the traditional angular measure of 17.86 mm of the Arthasastra.

Similarly the Harappan cubical weights show remarkable accuracy of standardisation. In the lower denominations, the system is binary: 1, 2, 1/3 x 8, 4, 8, 16, 32, and so on, up to 12,800 which is comparable with the traditional Indian ratio of 1:16 (one seer = 16 chhattacks). The unit is equivalent to 13.625 gm. In the higher weight denominations, the Harappans followed a decimal system, with fractional weights in one-thirds. 
They also were quite conversant with accurate ideas about circles, intersecting circles, squares and rectangles. A seal also shows four concentric engraved squares.

J.P. Joshi, writes in his Harappan Architecture & Civil Engineering (2008) that the Harappans had a good idea of geometry as revealed by the various structures constructed by them. They could divide a line into a given number of parts, drawing a perpendicular on a given line, transform a square into a rectangle of the same area, a parallelogram, a rhombus of equal dimensions, and so on.

The bricks, both sun-baked and kiln-burnt, are moulded in a rectangular shape and follow the ratio of 1: 2: 4 measuring 10 x 20 x 40 cm and 7.5 x 15 x 30 cm.

It is obvious that the Harappans paid due attention to water harvesting, use of underground water, drainage and sanitation.

Great skill was required to maintain the drainage system gradient at the time of building structures, which shows that the Harappans possessed the idea of levels and gradients. Smaller drains joined the big drains having sluices and proper gradients.

The Harappan architects were familiar with the basics of hydraulic engineering, which could not have been acquired overnight. The Harappan structures are similar to the gabarbands of south Baluchistan. Archaeologically, the gabarbands can be associated with the pre-Harappan settlements because of their geographical proximity. The gabarbands are made of huge boulders and cut-blocks across the gaps in the hills with broad catchments of ephemeral streams. The dams were used to store water for various purposes including irrigation. Sometimes, such constructions were raised to conserve soil and moisture.

Bathing facilities in every house indicate that washing, cleanliness and water ablutions were important to the Harappans. This legacy we have inherited from them. The numerous wells dug throughout the city (and maintained for several centuries) were sources of pure water, essential for effective cleanliness. The drainage system served to move effluents away from the houses, below ground (safely out of the way and out of sight), in brick-lined channels that prevented contamination of the earth and the city. When the early excavators had cleared some of these wells, these again began to fill with water, although much of the ground water around the site today is quite brackish.  These 10 -15 meter deep wells were lined with specially made wedge-shaped bricks to form a structurally round cylinder that would not cave in under pressure from the surrounding soil. On the top edge of the well, there are grooves on the bricks indicating that ropes were used to lift the water out. The drains for collecting rain water and those for taking away dirty sewage water were separate from each other.

Many neighbourhoods had public wells along the main streets, for use for animals and for the general public. At Mohenjodaro there were over 700 wells.  At Mohenjodaro and Harappa, bathing platforms with drains were often situated in rooms adjacent to the well, using tapered terracotta drainpipes to direct the water out on to the street. Harappa revealed latrines in almost every house. It is worth noting that there were garbage bins along the major streets, a civic concept which seems very modern but had originated in Harappan times. To top it all, the excavator of Dholavira, in Gujarat, has discovered a septic tank. This would be the first such sanitary device reported from anywhere.

The Great Bath

The Great Bath at Mohenjodaro is a bathing platform, raised to the civic level. It is larger and more complex than the household facilities. The Great Bath is a marvel of waterproofing engineering skill. According to Wheeler (1968: 41- 46), “To ensure that the bath was watertight, the floor was of bricks set on edge in gypsum mortar; the sides were similarly mortared, and behind the facing-bricks was an inch thick damp-proof course of bitumen held by a further wall of brick, which was in turn retained by mud-bricks packed between it and an outer backed brick wall.”

Water Reservoirs
Excavations at the Harappan site of Dholavira in Gujarat have revealed remarkable evidence of water harvesting and water storage structures. Most importantly, the system was made an integral part of the urban planning. About 10% of the town area was covered with underground reservoirs. Though Dholavira had drains and pipes for storm water, sewage and also for potable water, they were never intermixed.

The Legacy

In the early centuries of the second millennium BCE, one witnesses the curious phenomenon of the drastic break after the Mature Harappan Culture, and also the continuity of the cultural traditions. It is clear that the basic substratum of the Indian Civilisation is provided by the Harappa Culture.

The typical Harappan house plan of a central courtyard surrounded by rooms (it has been found by air-conditioning experts to be best suited for the Indian climate) seems to have continued from the Harappan times.  The binary system of weights of the Harappans followed 1, 2, 4, 8, 16, 32, 64. . .  128(x), with fractions in one-thirds.  Till recently, the Indian seer equalling 16 chhattacks and one rupee equalling 16 annas basically followed the same binary system. 

At Banawali was found a ‘touchstone bearing gold streaks of different hues’. This was evidently used to test the purity of gold. The same method is applied by goldsmiths even to this day! The medieval metallic mirror with a handle also goes back to the Harappan times. The toiletry gadget consisting of tweezers, a small pointed rod and a  flattish object (probably to remove ear wool) used today, has exact Harappan counterparts.
The tandoor, a typical cooking oven used in the north-western part of the Indian subcontinent, was found in the Early Harappan levels of Kalibangan.

Although broken terracotta models of ploughshares were reported from Mohenjodaro and Harappa, Banawali has now yielded an intact specimen.

The evidence of the use of bullock carts at the Harappan sites is provided by the terracotta models. The gauge of the ancient carts (1.08 m), as deduced from the ruts, is similar to that of the modern Sindhi carts. Similar ruts have also been found at Banawali. The modern ekka type of vehicle was also used by the Harappans, as indicated by a model in copper found at Harappa.

The Harappan legacy is not its city life, but rural technologies or peasant science, knowledge that was within the control and experience of the ordinary household or village – elements of culture that had been internalised and passed down for generations within the family and the community.

Prof. D.P. Agrawal is a distinguished scientist who worked earlier at PRL, Ahmedabad and TIFR, Mumbai. He is a Fellow of the National Academy of Sciences and is an expert on radio-carbon dating of archeological finds. He has written several books on the Harappan Civilisation, He is currently the Director of Lok Vigyan Kendra at Almora, Uttarakhand and is the General Editor of a series of monographs on History of Indian Science and Technology, published by the Infinity Foundation. 

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