Mohenjo-daro

The builders planned the city before they built it.

Straight streets crossed each other like lines on graph paper. Houses had small bathrooms. Drains under the streets carried dirty water away.

Mohenjo-daro was laid out in about a dozen big blocks, each about 384 meters long and 228 meters wide, divided by straight or bent lanes. Streets crossed each other at right angles.

Most buildings were made of baked brick. Most houses had small bathrooms, and both houses and streets had drains, so waste water flowed away. There were wells for fresh water and soak pits for sewage. Brick stairs show that houses had an upper floor or a flat roof people could use.

Britannica describes a city laid out with remarkable regularity into something like a dozen blocks, or 'islands', each about 1,260 by 750 ft (384 by 228 m), subdivided by straight or doglegged lanes. UNESCO notes streets intersecting at right angles, in a highly orderly plan that built in sanitation and drainage: wells, drains and soak pits for sewage.

The buildings are mostly of baked brick. In the lower town, substantial courtyard houses indicate a considerable middle class; most had small bathrooms, and houses and streets alike were well provided with drains. Brick stairs imply upper stories or usable flat roofs. Walls were originally plastered with mud, Britannica suggests, to limit the damage from salts in the bricks, which react destructively to changing heat and humidity.

On a high mound stood a giant bath. It was like a big pool, with a porch around it.

Diggers found little clay bulls. They found a gold necklace. They also found a small bronze dancer.

The city had two parts. To the west was the citadel, a mound raised 6 to 12 meters high with mud and mud brick, with some square towers of baked brick. On it stood the Great Bath, a large pool with a veranda around it, as well as a big granary for storing grain and halls where people gathered.

To the east lay the lower town of houses and streets. Archaeologists found many treasures: small clay figures of bulls and buffalo, jewelry of gold and stones, a stone carving of a bearded man and a famous little bronze figure known as the 'Dancing Girl'.

UNESCO divides the site into the citadel to the west, crowned by the later stupa, and the lower city to the east along the Indus. Britannica describes the citadel as the central western block, raised artificially 6 to 12 m with mud and mud brick and fortified, to an unknown extent, by square towers of baked brick. On its summit stood an elaborate bath or tank surrounded by a veranda, a large residential building, a massive granary and at least two aisled assembly halls; Britannica concludes that the citadel was the site's religious and ceremonial headquarters.

Architectural decoration is lacking, perhaps because it was in timber that has decayed, and stone sculpture is scarce, though it includes the head and shoulders of a bearded man wearing a cloak carved with trefoils once filled with red paste. Britannica calls the bronze 'Dancing Girl' the most notable figurative work; terra-cotta bulls and buffalo, figurines and gold-and-stone necklaces are also known.

The old bricks can be damaged by salt and water from the ground.

Workers protect the walls with a coat of mud. Most of the city is still under the ground, waiting to be explored.

The ruins cover 240 hectares, but only about one third has been dug up since 1922. The rest is still buried.

Today one big danger comes from below. Water from the river rises in the ground and carries salt into the old bricks, which slowly crumble. In the 1970s, UNESCO led an international campaign to help. Workers still protect the walls by covering them with mud, filling gaps and strengthening foundations. Banks of earth help guard the site against floods.

UNESCO notes that the burnt-brick structures cover 240 ha, of which only about a third has been excavated since 1922. Rising groundwater from the Indus has carried salts into the foundations, the subject of a UNESCO international campaign in the 1970s that partly reduced the damage to the mud-brick buildings.

The Culture Department of the Government of Sindh, responsible for the site since the 18th Amendment of 2010, runs a site office with a scientific laboratory. Conservators counter salt action, thermal stress and rain with mud slurry, mud capping, re-pointing and underpinning, keeping to traditional methods to preserve authenticity. Embankments and spurs reduce flood risk, though UNESCO warns that a breach of the dam upstream would be catastrophic, and that the setting is vulnerable to nearby development.