The drains and baths of Mohenjo-daro

The story

The home bathroom, 4,500 years ago

Step in your imagination into a house in Mohenjo-daro around 2500 BC. From the narrow lane you go through a door into a central courtyard, around which the rooms open. In one corner there is a well lined with fired bricks, from which water is drawn. Nearby, a small room has a brick floor sloping slightly: this is the bathroom. You wash by pouring water from a jug, and the water slips away through a hole in the wall and ends up in a clay pipe or a small channel. The channel leads into a drain that runs under the street. In some buildings there is even a toilet, with a seat and a duct that carries the waste into the sewer.

This is not an imaginary scene. Archaeologists have found hundreds of houses with these fittings. At Mohenjo-daro about seven hundred wells have been counted, one for every three or four houses. No other city of that time had so widespread a system of clean water and dirty water.

Under the streets

The heart of the system was the sewers. Along the main streets ran channels of fired brick, covered with slabs of brick or stone that could be lifted for cleaning. At regular intervals there were inspection pits, which served to hold back debris and let the water through. The drains of the houses flowed into those of the street, those of the street into larger channels, and finally the used water left through the walls, towards the fields or the river. To build them, the bricks were joined with a mortar of mud or gypsum and, where needed, with bitumen, a waterproof black substance.

This system demanded an overall plan: houses had to face inwards, with blank walls on the street, and the slopes of the channels had to be carefully calculated so that the water would flow. Someone in the city had to decide and enforce the rules and then pay the teams who cleaned the drains. It is one of the reasons why scholars think the Indus cities were governed with great care, even though we do not know who governed.

The Great Bath

At the highest point of Mohenjo-daro, the citadel, there is a unique building: the Great Bath. It is a rectangular pool about twelve metres long, seven wide and two and a half deep, lined with fired bricks joined with gypsum. Between two layers of bricks the craftsmen put a layer of bitumen, to stop the water seeping into the ground: after 4,500 years, the seal is still good. You went down by two flights of steps, one to the north and one to the south, and around it ran a colonnade with rooms. The water came from a nearby well and was drained through a channel with a corbelled vault, high enough to let a person crawl in.

What it was for, nobody knows for certain. Most scholars think of ritual purification baths, like those that still exist today in the religions of India, but this is a hypothesis: we have no texts that say so, and we do not know what the inhabitants believed. It is not even certain whether it was a public pool or a place reserved for priests.

Nothing like it elsewhere? Not quite

It is often read that Europe had sewers like these only many centuries later, and that is true in general. But we must be precise: ancient drainage systems are found elsewhere too. At Skara Brae, in the Scottish Orkney Islands, houses about 5,000 years old had a kind of channel for waste. The palace of Knossos, in Crete, had pipes and bathrooms around 1700 BC. The difference is that at Mohenjo-daro the system served almost a whole city of tens of thousands of inhabitants, not just a palace or a village.

Sewers, afterwards, had a strange history. The Cloaca Maxima of Rome, built in the 6th century BC, is the most famous of antiquity. But after the fall of the Roman Empire, in many European cities the systems were lost. To see orderly and widespread systems again we have to wait for the nineteenth century: in London, after the “Great Stink” of 1858, the engineer Joseph Bazalgette built more than 1,800 kilometres of sewers. That is, over 4,000 years after Mohenjo-daro.

A city to protect

Today Mohenjo-daro is in danger. After 4,500 years the bricks are crumbling from the salt rising from the ground and from rain and floods. The site was added to the World Heritage list in 1980 and is the subject of conservation work. Only a part has been excavated, and archaeologists have decided to leave the rest underground, because it is safer: an excellent way of keeping something for future generations.