As many followers say, you should spend a moment of your time watching this video. This is a great restored German bunker built in Denmark during World War II. May be one of the best videos of this youtube channel. It's amazing to see someone has taken the time to preserve history and not destroy.

You should recognize that Germans were excellent bunkers' builders. You can see the inner working, other than bare walls as in most you find. 

It's an amazing work. Congratulations WW2HistoryHunter!