Answer: The Indus Valley lay forgotten and undiscovered for thousands of years. In 1826, a British traveller in India called Charles Masson came across some mysterious brick mounds. He thought they looked like old castles, but didn't know who built them.
The two best-known excavated cities of this culture are Harappa and Mohenjo-daro (located in modern-day Pakistan), both of which are thought to have once had populations of between 40,000-50,000 people, which is stunning when one realizes that most ancient cities had on average 10,000 people living in them
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