14th century, 40 m high,
built to be used as a prison.  Symbol of the judicial competence of the archbishop in the Middle Ages, storehouse for the archives of the Chapter of the Cathedral under the Old Regime, the tower became again a prison for the convicts under the Terror and for the opponents to the Coup of 2nd December 1851 and to the establishment of the Second Empire, who were banned to Algeria.

Each of the 7 floors of the upper part forms a cell, the highest being the only one opened to the four points of the horizon.