This majestic octagonal tower built in the 15C is in fact a lookout tower, which has preserved the arch that joined it to the wall. It was alternately a prison and an astronomical observatory. Its name comes from a legend that tells how a husband, furious that his wife would not fulfil her conjugal duties, killed her with his own hands. The sentence the king ordered was for the husband to build this tower in memory of his wife, whom he had killed in such an undignified way, hence the expression mal muerta.