Haapsalu Castle — Wikipedia

Haapsalu Castle (also Haapsalu Episcopal Castle, Estonian: Haapsalu piiskopilinnus, or more simply Bishop's Castle) is a castle with cathedral in Haapsalu, Estonia, founded in the thirteenth century as the seat of the Bishopric of Ösel-Wiek. According to legend, during full moons in August, an image of a maiden, The White Lady, appears on the inner wall of the chapel.