The rock of.Gibraltar had a secret Stay Behind cave for Hitler's invasion. https://www.amusingplanet.com/2017/06/operation-tracer-secret-plan-to-bury.html?m=1

The rock of.Gibraltar had a secret Stay Behind cave for Hitler's invasion. https://www.amusingplanet.com/2017/06/operation-tracer-secret-plan-to-bury.html?m=1 https://www.amusingplanet.com/2017/06/operation-tracer-secre... It was not found until recently. They also found one of secret operatives alive (doctor). https://www.google.fi/amp/s/www.warhistoryonline.com/world-war-ii/operation-tracer-british-cavemen.html/amp?espv=1 https://www.google.fi/amp/s/www.warhistoryonline.com/world-w...