https://en.wikipedia.org/wiki/Owl_Mountains
https://en.wikipedia.org/wiki/Project_Riese:
http://www.thirdreichruins.com/riese.htm
https://www.google.ca/search?biw=1276&bih=671&q=owl+mountains+germany&oq=owl+mountains+germany&gs_l=serp.12..0i30.7234.7234.0.8668.1.1.0.0.0.0.69.69.1.1.0....0...1c.1.64.serp..0.1.69.F2QCmIfo2gI