Mohenjo-daro — Bronze Age City of 40,000 People

Mohenjo-daro, located in present-day Pakistan, was one of the largest cities of the ancient Indus Valley Civilisation, home to an estimated 40,000 people around 2500 BCE. The city featured a sophisticated grid street layout, a large public bath (the 'Great Bath'), multi-storey brick buildings, and an advanced drainage system that was among the world's first urban sanitation networks. The Indus script found on thousands of seals and tablets has yet to be fully deciphered, making Mohenjo-daro one of history's greatest unsolved puzzles.

Population estimates range widely; some scholars suggest 20,000–40,000 or higher. The city's sudden decline around 1900 BCE is not fully understood.