Blåtårn

The Blåtårn (literally "Blue Tower" in Danish) is a name associated with multiple locations and concepts in Danish folklore and history. It most commonly refers to the tower of Copenhagen Castle, a royal residence that stood in Copenhagen from the late 14th century until its demolition in the 18th century.

The Copenhagen Castle's Blåtårn was notorious for being a prison tower. High-profile prisoners, often political dissidents or those who had fallen out of favor with the monarchy, were held there under harsh conditions. Stories and legends associated with the Blåtårn depict it as a place of misery, torture, and even supernatural occurrences. Accounts of unexplained sounds, apparitions, and other paranormal phenomena were widely circulated, contributing to its grim reputation. Leonora Christina Ulfeldt, daughter of King Christian IV, was one of the most famous and long-term prisoners held within its walls, and her writings detailed her experiences within the tower.

The term "Blåtårn" can also refer to similar prison towers in other medieval castles or fortifications, although the one in Copenhagen Castle is the most widely known and historically significant. The term became synonymous with imprisonment and suffering, and continues to be used metaphorically in Danish to describe a state of oppression or confinement.