I found this museum totally by accident. I got lost (as a local) in the narrow streets of the castle with a smartphone in my hand. Fortunately I found this place, which we visited on the weekend with a group of friends.
The museum is a hospital which operated during WWII and later on it functioned as a nuclear bunker. They are located on the road which leads to the citadel, in the bottom of the castle. Not a crowded tourist route at all. They don’t have any advertisement and it’s not marked with any signs due to the fact this is forbidden in the historical Buda Castle area. They say this is why they’re not overwhelmed with visitors.
They offer guided tours in small groups in more languages, we took English because my wife is non-Hungarian. The young lady giving the tour was so passionate and obviously loved her job. Her English was excellent!
I thought I was well educated on the history of Budapest but they surprised me. I learned, and saw, so many interesting things. One of my doctor friends was also surprised by how great a job they’ve done in saving this part of the city!
Check their tickets, they reminded me that’s there’s a 50% discount for those under the age of 25.
Totally satisfied! Hidden gem!