Is Houska Castle haunted?
Czechia Reported haunting level 5 of 5

What actually happened
German forces seized the castle from 1939 to 1945 and used it as a repository for confiscated Jewish and Masonic books.
The history
Founded in the first half of the 13th century under Přemysl Otakar II on a 9th-century hillfort, the castle was bought by Škoda president Josef Šimonek in 1924 and opened to the public in 1999.
What people report
The castle's own telling has it built over a passage to hell with the chapel set above the chasm, and a faceless figure in a black monk's hood is said to watch those who visit at night.
That paragraph is reported tradition, not a claim about what is there. The history above it is sourced; the stories are recorded because people tell them.
Visiting
Houska 1, 471 62 Okna, Czechia