Château de Brézé is a small castle by European standards. Occupying less than 2 acres, this modest U-shaped building surrounded by a dry moat appears nothing out of the ordinary. But beneath its humble foundation lies one of Europe’s largest underground fortress.

Château de Brézé is located on the outskirts of the small village of Breze, in the Saumur region of the Loire Valley, France. It was built by Arthus de Maillé-Brézé, the then lord of the castle, in the mid-16th century. Fearing invasion from enemies and marauding Vikings, Maillé-Brézé had a large bunker built directly beneath the castle, containing living spaces, storage areas, and other amenities. These are connected by more than 3 kilometers of tunnels.

Photo: Martin Burns/Flickr