Museum Podziemny kompleks Riese Włodarz in Głuszyca

You're standing at Włodarz, a mountain in the Owl Mountains of southern Poland. It looks quiet and wooded, but inside it runs a grid of tunnels more than three kilometres long. This is one of seven underground complexes of Project Riese, German for 'giant'. Nazi Germany had them carved out between 1943 and 1945, when this area was German. Today it's Poland.