The drainage system found in the Harappan cities was very well planned. There was a gentle slope for the water to float down the drains. They were also covered and inspection holes were provided at intervals to clean them. Probably all drains, streets and houses were planned and build at the same time.

Drainage System in the Earliest Cities
Drainage systems were crucial in the earliest cities to manage wastewater and prevent flooding. Here is a detailed explanation of the drainage system in the earliest cities:

1. Importance of Drainage System
- The drainage system was vital for maintaining cleanliness and preventing waterborne diseases in ancient cities.
- It helped in managing and disposing of wastewater from households and public areas.

2. Components of Drainage System
- In the earliest cities, drainage systems consisted of underground drains made of clay, stone, or brick.
- These drains were connected to street gutters that carried wastewater away from the city.

3. Functionality of Drainage System
- Rainwater from roofs and streets would flow into the street gutters, which were sloped to allow the water to drain away.
- The underground drains would carry the wastewater to larger channels or rivers outside the city.

4. Maintenance of Drainage System
- The maintenance of drainage systems was essential to prevent blockages and ensure proper functioning.
- City authorities or residents would regularly clean the drains to avoid clogging.

5. Evolution of Drainage Systems
- Over time, drainage systems in cities became more sophisticated with the use of aqueducts, sewers, and underground vaults.
- These advancements improved sanitation and hygiene in urban areas.
In conclusion, the drainage system played a crucial role in the earliest cities by managing wastewater and promoting cleanliness. It was an essential infrastructure that contributed to the development and sustainability of urban settlements.