4500-year-old urban planning at Mohenjo-daro

For most Westerners, the term “ancient civilization” evokes images of ancient Rome, Greece or Egypt. Much less known is the Bronze Age Indus Valley civilization that flourished from 2500 to 1800 BCE in areas on modern-day Pakistan and northwest India. Yet it was the largest civilization of its time with a population estimated at 5 million people. Archeologists have uncovered more than a 1000 sites of the Indus Valley people, and the most famous ones are the cities of Mohenjo-daro and Harappa in Pakistan.

I had the opportunity to visit Mohenjo-daro earlier this year, and I was inspired by how much these people could achieve with so little so long ago. In its heyday, Mohenjo-daro had a population of 40000 people and it was the most advanced city in the world in terms of urban planning and especially sanitation. Despite being such an impressive site and on the UNESCO World Heritage list, the site receives very few foreign visitors today because of the unpredictable situation in Pakistan. I see Mohenjo-daro today as a reminder of how simple technology and materials can be used to provide the most basic human needs.

view of Mohenjo-daro
Mohenjo-daro, meaning “the Mound of the Dead”, was named after the Buddhist stupa that dominates the site today. The stupa is in fact a much newer construction, built on top of the buried Bronze Age city.

The on-site Mohenjo-daro museum displays a number of practical and recreational artifacts found during excavations. Among the most interesting  finds are a large number of carved seals that depict different animals and the local writing that still hasn’t been encrypted. Another interesting fact is the near lack of weapons or other evidence of warfare, suggesting a peaceful civilization.

Seals from Mohenjo-daro museum
Seals on display at the on-site Mohenjo-daro museum, showing the local script.

Equality and comfort in city planning

Walking among the remaining brick walls of Mohenjo-daro makes one marvel at how planned the city looks. There is a lack of ornamentation and the design of the city and the houses focused instead on creating a comfortable and clean urban environment. There was also little difference in living conditions between the rich and the poor which suggests a level of equality in the society.

Artist's view of Mohenjo-daro
An artist’s view of Mohenjo-daro in its heyday.

The climate around Mohenjo-daro is very hot most of the year and the design of the city takes advantage of wind and differences in day and night temperatures to create a more comfortable microclimate in the city. Except for a few main streets, the streets are narrow and have high walls that provided efficient shading and protection from the sun. The streets were laid in a perpendicular grid which minimized the amount of obstructions and encouraged air flow through the streets, providing a comfortable cooling effect.

The houses had thick walls made of baked bricks and most houses had two stories. The uniform size and shape of bricks found at different Indus Valley sites suggests that standardized sizes were used. The light color of the bricks would reflected the heat from the sun, and the heat from the air was absorbed by the thermal mass of the walls, keeping the houses and the streets cool during the day and warm during the night.

The houses had very few window openings and these were mainly towards the smaller side streets or interior courtyards around which rooms were arranged. This way the air that entered the houses came mostly from the cooler shaded areas. The near lack of openings and the thick walls kept the houses cool, but the lack of air movement might mean that people spent most of the day outdoors. Evidence shows that the roofs were most likely flat rammed earth. Clay plaster was used for waterproofing the roof and remains of clay roof drains have also been found.

Streets of Mohenjo-daro
Well shaded streets provided an escape from the heat.

Forerunners in urban water and waste management

Like most ancient civilizations, the Indus Valley civilization was centered around a river, in this case the Indus river, and the river provided the element without which no human settlement could be possible – water. The climate around Mohenjo-daro is semi-arid with little rainfall, and this makes access to water an even more crucial issue. Instead of relying only on surface water from the river, the city had a large number of wells, both public wells and also private wells located in courtyards of houses, and these made water easily accessible in the urban setting.

Well in Mohenjo-daro
Wells provided water for households in the city while the nearby Indus river provided water for agriculture.

The importance of water is further reflected in the largest building of Mohenjo-daro. Unlike the majority of historic sites, the largest building was not a temple, a palace or a tomb, but instead a bath house, known as the Great Bath. The floor of the Great Bath had a gentle slope that slowly drained the water out of the bath and into a drainage system and eventually out of the city, meaning that fresh water was constantly provided to keep the bath clean. Gypsum was used for waterproofing the floor and the side walls, and the side walls also have a layer of bitumen for further waterproofing.

Great Bath of Mohenjo-daro
The scale and detailing of the Great Bath shows how important water was for the society, and the Great Bath was probably even used for religious purposes.

Probably the most impressive urban feature of Mohenjo-daro is its sanitation system. The city had an extensive covered drainage system that relied on gravity and carried sewage out of the city. The drains were running under the streets and they had manholes with brick tiles that could easily be removed if the drain needed inspecting.

Houses had bathrooms that were directly connected to the drainage system. Evidence shows that water was used to flush toilets and that water was also used to wash up afterwards, showing an early understanding of hygiene. Some bathrooms were even on the second floor and these were connected to the drainage system through pipes running inside the brick walls. Some houses also had garbage chutes for other types of waste.

Drainage system of Mohenjo-daro
A part of the extensive covered drainage system.

Considering that the Indus Valley people could provide urban sanitation 4500 years ago, it seems incredible that there are today 1.2 billion people whole have no access to sanitation and rely on open defecation.

The decline of Mohenjo-daro – then and now

It is still a mystery what led to the decline of Mohenjo-daro and the whole Indus Valley civilization. Theories mention invasion or natural disasters such as floods caused by changes in the course of the Indus river. A more pressing question however, is the decline of the site today.

Excavations at Mohenjo-daro began less than a hundred years ago, and yet the structures that survived millennia have been severely damaged during this time. The structures are eroding and collapsing due to improper restoration, neglect, looting, and salt from the groundwater. Experimentations in restoration have actually made things worse and some archeologists believe that the site will not last another 20 or 30 years at this rate of decline.

Erosion of bricks in Mohenjo-daro
A wall showing how the bricks are degrading.

At the same time only about 10% of the vast site has been excavated. Many of the remaining parts are below the water table today because of changes in the course of the Indus river, and this makes these parts difficult to excavate. Considering the damage done to the excavated parts, it might be better to leave the remaining parts alone so that the heritage can be passed on to future generations who can hopefully better understand and appreciate it.

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