The former steelworks ARBED, now known as ArcelorMittal, operated a number of mines in the Grand Duchy until the early 1980s, with a network of open pits and underground tunnels.
The last mine was closed in Thillebierg, Differdange, over 40 years ago. Nowadays, this old tunnel is home to a colony of bats. RTL's Christophe Hochard visited the historical site to see how it became a habitat for its current airborne residents.
