The previous structure of today’s Prison Tower (Käfigturm) was completed in 1256 and served as a fortified tower for the City of Bern. When the city was extended up to the Church of the Holy Ghost (Heiliggeistkirche) in 1345, the tower lost its function.
After the great fire of 1405, the Prison Tower was used for holding prisoners for the first time. The old tower was torn down in 1641 and replaced by today’s tower which was completed in 1644. Following the completion of the new prison in the District Office in 1897, the tower was repurposed into a government archive for the Canton of Bern. Since 1999, the Prison Tower now serves as the seat of the Confederation's political forum, hosting exhibitions and events relating to political issues.