Orny, Italy
The Feste Prinz Regent Luitpold, renamed Group Fortification Yser after 1919, is a military installation near Metz. It is part of the second fortified belt of forts of Metz and had its baptism of fire in late 1944, when the Battle of Metz occurred.
Listen to the audio guide for Group Fortification Yser Free on WIP — starts by itself when you arrive, even with the screen off