The two most unique hotels I've ever stayed in:
Yanggakdo Hotel, Pyongyang, North Korea.
1. The hotel is on an island. No one is allowed to exit the hotel without a local guide.
2. There are some secret floors that are not accessible to tourists like the notorious 5th floor. Caution: Going there can lead to death! Otto Warmbier - Wikipedia
3. The only hotel in the world that shows a week-old world news in the room television. Interestingly there is a dedicated rebroadcast floor in the hotel.
4. The only hotel that could not think of a restaurant name. You can find No 1 Restaurant. Also, No 2 and No 3!
5. The only hotel where you can find unique services like a post office and a tailor!
6. The hotel was built in the 90s. It is well maintained but has some old stuffs like this AC control from the past.
Grand cave suites, Cappadocia, Turkey.
Staying in a cave hotel is a must to experience this mystic, rusty and beautiful town en route the ancient silk route.
From the outside it looks something like:
And from the inside: