The tower may have been built before the official arrival of the bishop in 1244 and was part of the defensive system of the first rampart.
Built entirely of tuff, limestone rock that the hill is made of, you could originally access it through a removable wooden staircase and a door on the 1st floor.
Many openings were added: pointed arches of white limestone and modern rectangular windows.
At the end of the 14th century, the tower was connected to the rest of the palace by three slightly pointed arches.