UK Man Renovates Medieval French Château, Finds Vast Tunnel Network Used by the Resistance During WWII

Young couple renovate a crumbling French chateau

In France, workers build a castle from scratch the 13th century way : NPR

The Tunnels of Halifax – Fact and Fiction: A Brief and Not at All Definitive History

Revival Medieval Evelyn Wallace -The Castle Lady

The secret charm of Lower Silesia

The secret charm of Lower Silesia

Paris Development May Transform Historic Tunnel Network - Bloomberg

Charming small towns that hide amazing underground worlds

Tintern 'secret' medieval tunnel system found by accident - BBC News