We had a blast in Slovenia a few weeks ago. Beautiful and extremely varied landscapes, very, very nice people, and they even make good wine...
Here is Predjama Castle. As far as I understood, it means something like "in front of the caves". The castle is indeed just a facade hiding kilometers of caves. it had the reputation of being untakable, it is really difficult to access.
We visited during the day, and I went back at night for a series of long exposures.
The place is very dark at night, and I was amused to see a few tourists try to approach around midnight but finally run away! As the castle is mostly open it is accessible to birds and there are many frightening noises for unprepared minds...
The milky way shot is a panorama of 8 pictures, taken with my X-T1 and Samyang 12mm f/2. The milky way should of course be straight but the panorama added some curvature.