The Great Bath is the most famous structure at Moenjodaro and one of the most remarkable ancient structures in South Asia. Measuring 12 metres by 7 metres, with walls still standing to nearly a metre, it was built around 2600 BC with a sophisticated waterproofing system of bitumen-sealed bricks. Steps at either end lead down into the pool. Around it ran a corridor and a series of smaller rooms — perhaps changing rooms, perhaps the quarters of priests.
What makes the Great Bath striking is not just its age but its sophistication. The Indus Valley Civilization built public infrastructure at a scale and quality that would not be matched in much of the world for another two thousand years. Stand at the edge and consider that the people who used this bath were contemporaries of the Old Kingdom Egyptians and the Early Dynastic Mesopotamians — and arguably building more equitably, with no palaces and no apparent kings.