This 29m-high Gothic tower was built during the Hundred Years' War by the Duke of Bourgogne so that he could take refuge from his enemies – such as the supporters of the Duke of Orléans, whom he had assassinated. Part of a splendid mansion in the early 15th century, it is one of the few examples of feudal military architecture extant in Paris. Climb 140 steps up the spiral staircase to the top turret (no views).