I visited La Coupole (Wizernes), not far from Calais, a few years ago and would strongly recommend the trip. It is an amazing feat of engineering, despite it's death dealing purpose. But a terrible crime that it was built by slave labour and hundreds died during it's construction. Next time you're buying cheap booze across the "moat", vsit the place.
The slave labour survivor's piece in the Op Crossbow programme was very moving. And we think animals are cruel!