Laser surveys lead the team to undiscovered jungle temples. A dirt bike mission to a mountain city holds clues to the origins of the empire and in Laos, ground penetrating radar reveals how kings take new territory. Could a huge jungle pyramid also expose the makings of a mysterious cult?

The team use drones to explore one of the world's largest ancient water systems. Monsoon floods almost thwart the hunt for a lost mega-quarry, and ancient weapons, hidden battle carvings and traces of a colossal iron industry reveal the truth behind the awesome power of the Khmer military.