Porto Santo Stefano, located in the northern part of Monte Argentario, is the main center of this promontory. Due to its favorable geographical position it was frequented by the ancient peoples who sailed in the Mediterranean. The Romans left notable traces of their presence, including the remains of the baths of Domitian and in their maps indicated the locality with various names, such as Portus Traianus and Portus ad Cetarias. Under the domination of the Sienese which goes from the beginning of the 15th to the middle of the 16th century, the place became a landing place of little importance subject to frequent pirate raids. In this period the Argentiera tower was built in 1442, and some coastal towers. The development of the center began around 1550 under the Spanish governorate of Núñez Orejón de Ávila, and continued after the creation of the Presidi state and the construction of the Spanish fortress.