From 1496 to 1781, while it was first designated as the Cannon Tower, it was soon assigned as the prison tower. A fire in 1781 that damaged the upper floor marked a stop to the prison function of the tower. However, when in use, the dungeon and torturing methods were utilized to punish prisoners.
Today’s access to the tower is possible to those who have a Prague Castle Complex ticket. Once you walk down the stairs, the basement exposes torturing tools next to a caged skeleton. It is next to the Golden Lane.
The sad and troubling story of the first inmate affected many. First, his name was Dalibor of Kozojedy and he was convicted for helping rebels in his area. Second, while confined, he received a violin that he started playing. It attracted people who brought him food and sympathy. It is unclear to me if his playing the violin was to cover the sounds of torturing instruments. Nonetheless, and thirdly, it has inspired the Czech opera Dalibor. The knight was condemned to death and executed next to the tower that now carries his name: Daliborka.