Hohlgangsanlage 8 (often abbreviated to Ho8, and also known as the German Underground Hospital or the Jersey War Tunnels) was a partially completed underground hospital complex Jersey. It was built by German occupying forces during the occupation of Jersey during World War II. Over 1 km of tunnels were completed. After the liberation of the Channel Islands, the complex was converted into a museum detailing the occupation.

 

https://www.jerseywartunnels.com/

 

https://en.wikipedia.org/wiki/Hohlgangsanlage_8