This majestic octagonal tower built in the 15C is a lookout tower which has preserved the Arch that joins it to the wall. It was alternately a prison for the nobility and an astronomical observatory. Its name comes from a legend which tells how a husband, angry because he had a wife who would not fulfil her conjugal duties, killed her with his own hands. The king sentenced him to build this tower in memory of his wife killed in such an unworthy way hence the expression mal muerta.