The Lantern tower. (or Four Sergeants tower)
This tower served as a light house. It was also a prison, lots of English sailors spent time there. Carved into the floor on one of the levels is a chess board (one way to pass the time). There is also plenty of graffiti. One is a carving of a sailing ship, it's very beautiful and gives a lot of information to historians. It was also known as the Priest's tower, during times of religious conflict, priests were thrown off. I think a few unfortunate sailors met their fate that way too. The romantic title is the Four Sergeants tower. They were rebels who were executed. No one is sure whether there were four and they might even have been taken to Paris to be executed!