Up to 10 million sandstone blocks, perfectly oriented to mirror the cosmos: Angkor Wat is a 400-acre scale model of the Hindu universe, with five towers for the peaks of Mount Meru and a moat for the cosmic ocean. But the world's largest religious complex is not a static ruin. It is a machine that has reinvented itself for 900 years, and its strangest existential threats today include viral video tourists and the town next door's plumbing.

This episode tears up the blueprints: why the temple faces west toward death when nearly every Khmer temple faces east, the counterclockwise carvings that suggest a king's mausoleum, and the rival theory that the whole complex is an astronomical clock. It follows the Buddhist conversion that walled in Vishnu's shrine, the fortress years, the French plaster-cast spectacle, and the modern dilemma of a sacre ...