The Infamous Tour de Nesle

There is a pedestrian bridge across the Seine that links the Louvre with the domed Institut de France, home to the Académie Française (the modern-day French language police). But for 450 years, from 1210 to 1663, the site was the location of the notorious Tour de Nesle (pronounced “TOO-er duh NELL”). This medieval tower was constructed to stave off a possible attack by the English, but became royal property in the 14th century. It was also home to a scandal of enormous proportions.
The wives of the three sons of Philip the Fair (regent 1285-1314, and named for his matinée-idol good looks) used this tower for flirtatious liaisons, since they were left pining away by their husbands for extended periods. When these light-hearted affairs burgeoned into outright adulterous relationships, the princesses were implicated, and their lovers tortured, castrated, decapitated, hung by the armpits and then left to rot. Two of the princesses had their heads shaved and were imprisoned. One was subsequently suffocated by order of her husband, and the other perished in her dank cell, pregnant by her jailer; both died while still in their twenties. The third, however, was never proven guilty and was released and even allowed to accede to the throne as the wife of Philip V. She outlived her husband and spent her remaining years in merry widowhood, during which time she once again made good use of the Tour de Nesle. Her habit was to lure a student up into the tower to serve her needs, then tie him up in a sack and send him plunging into the Seine below, thus ensuring that she could not be implicated in a scandal (she was a quick learner).
One of them, a chap named Buridan, actually survived the fall, as he landed on a barge full of hay. He subsequently got himself involved in another relationship that came to a head in a duel and the near death of his rival. This incident would have been just a footnote in the sordid history of medieval Paris, except that Buridan went on to be appointed the Rector of the University of Paris, and his rival became Pope Clement VI.
Metro: St-Germain des-Prés
The photo below shows the plaque on the domed Institut de France, indicating the location of the Tour de Nesle.