Karosta Military Prison in Latvia
Karosta Prison sits in the North end of Liepaja, Latvia, a very small and sad town. When the hammer & sickle flag flew over Latvia, Karosta was a military compound housing over 40,000 military personnel. The prison itself was once a hospital and was used mainly for Russian soldiers.
Now, tourists can go on a tour and even spend the night here for a reasonable sum. The coolest part of the tour experience was seeing all the Soviet Era propaganda and graffiti written on the walls.
For overnighters, you can sleep in an actual cell and guards will yell at you. Unfortunately, there are no creature comforts here like wifi or freedom, so you must suck it up for the evening if you want to stay.