Picture a metropolis of 40,000 people built 4,500 years ago — with flush toilets, a perfect grid of streets, and rulers carved with hair's-breadth precision. Now notice what's missing: no palaces, no grand temples, no obvious evidence of a single all-powerful king.

This episode uncovers Mohenjo-Daro, a crown jewel of the Indus Valley civilization that was lost for 3,700 years and fundamentally challenges what we expect an ancient society to look like. We explore its astonishing engineering, its contested artifacts, and the slow ecological collapse that may have erased it.

• How a single flint scraper spotted beneath a later Buddhist stupa in 1919–20 pushed the site's timeline back by millennia and triggered the great excavations.
• Civic marvels over royal monuments: the bitumen-waterproofed Great Bath, the misnamed "Great Gr ...