In 1300 CE, Angkor was possibly the biggest city in the world. It had – and still has – the largest religious monument in the world, Angkor Wat. It was the seat of kings, home to an empire for 600 years, an incredible feat of urban engineering in a flood plain and rainforest. Then it was abandoned, left to the jungle and a handful of farmers and monks for hundreds of years. Centuries later, what happened to the city of Angkor is still a mystery. There are no graves. No bodies. Not a single bone has been found from the millions who lived there over centuries. But Angkor has left secrets buried in the mud underneath the city of water that reveal visions of the grand civilization.