At first sight, there is little clue to the secrets that lie beneath the Château de Brézé in France. But below the surface of this impressive castle lies a deep network of tunnels and rooms that together form one of Europe's largest underground fortresses.
Much like the billionaires of today, the lords of this castle carefully constructed themselves a medieval 'doomsday bunker' to provide themselves with shelter and protection in the face of invasion or disease.
Video by Mathieu Orcel and Augustin Muniz
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