How the Indus Valley Built the World's First Planned Cities
Around 2500 BCE — nearly 4,500 years ago — the city of Mohenjo-daro in the Indus Valley had something most ancient cities didn't: straight streets laid out in a perfect grid, and covered drains carrying dirty water away from every house. While other early cities grew in messy, winding patterns, Indus Valley builders planned theirs out in advance, like drawing a map before laying a single brick.
What You'll Learn
- Explain why Indus Valley cities were built on a grid pattern - Describe how the ancient drainage (sewer) system worked - Explain why Indus Valley bricks were made to a standard size - Identify at least one major structure found in Mohenjo-daro and its purpose
Streets in a Grid: Planning Before Cars Existed
Mohenjo-daro and Harappa, the two largest Indus Valley cities, were built with main streets running north-south and east-west, crossing each other at right angles to form city blocks — very similar to how many modern cities like New York are laid out today. This grid design made it easy to travel through the city, deliver goods, and organize neighborhoods by trade, such as areas for potters or metalworkers. Archaeologists believe city planners decided on this layout before construction began, rather than letting the city grow randomly over time.
The World's Oldest Sewer System
Nearly every house in Mohenjo-daro connected to a covered brick drain running beneath the street, carrying wastewater away from homes and out of the city — a level of sanitation that wouldn't be matched in most of the world for thousands of years. Many homes even had their own private bathrooms and wells, something rare in the ancient world. Historians believe this careful attention to clean water and waste removal helped protect residents from the spread of disease.
Bricks Built to a Standard
Indus Valley builders made fired mud bricks in a strict ratio of 4:2:1 (length to width to height) at nearly every site across the civilization, whether a building was in Mohenjo-daro or a smaller town hundreds of miles away. This consistency suggests a shared building standard used across the entire Indus Valley civilization, which stretched over 1,600 kilometers. The Great Bath, a large watertight pool at the center of Mohenjo-daro built from these standardized bricks and sealed with natural tar, may have been used for public bathing or religious rituals.
Archaeologists have found thousands of Indus Valley seals carved with symbols, but nobody has fully translated the Indus script yet — so much of what these city planners were thinking remains a mystery.
Match each Indus Valley city feature to its purpose.
Terms
Definitions
Drag terms onto their definitions, or click a term then click a definition to match.
What was unusual about how Mohenjo-daro's streets were laid out compared to many other ancient cities?
Why is the Indus Valley's drainage system considered so advanced for its time?
Design Your Own Planned City Block
On graph paper, draw a 6x6 grid representing one section of an ancient city. Include: at least 2 straight streets crossing at right angles, a covered drain running along one street, at least 4 house plots, and one public building (like a granary or bath). Label each feature and write 2 sentences explaining one planning decision you made and why.
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