Castle built atop a Fortress - Château de Brézé - Bellevigne-les-Châteaux, France - Beneath its foundation lies one of Europe's largest underground fortress - Connected by more than 3 kms of tunnels
Underground passage castle hi-res stock photography and images - Alamy
Escape to the 800 year old Chateau du Masgelier in France - The Good Life France
The Ultimate Guide to Paris Underground (by Locals!)
Tour the inside of Lachlan Murdoch's new $150 million LA mansion
Best Kept Secrets of Versailles
The Secret Tunnels of Dover: A Hidden Piece of World War II History
Seeing inside secret hidden Tunnels underneath our French Chateau (what did we find!)
Secret tunnels hiding in real homes
What's Behind That Hidden Door?: The History of Hidden Doors– Murphy Door
Revealed: The Underground Secrets of the Buildings We Thought We Knew - Architizer Journal
This Medieval French Castle Is Hiding Almost Two Miles Of Secret Tunnels (& You Can Visit Them)
Beneath This Medieval German Town Lie Over 25 Miles of Forgotten Tunnels, Travel
A Secret World Hidden Beneath the Vineyards of Champagne