Its origin dates back to the tenth century, when a church-fortress was built on a Muslim mosque using the remains of a Roman building that was located nearby. Its construction was ordered by Alfonso X The Wise, who fortunately wanted to keep the inside of the building, keeping the mihrab (the Muslim prayer tower) intact. Later, the castle was used for defending themselves against the attacks from North Africa.

The ownership of the castle passed from hand to hand until Alfonso Pérez de Guzmán el Bueno donated it to his daughter Leonor de Guzmán in her marriage to Louis of Spain, giving rise to the house of Medinaceli, who would become the Lords of the Villa.
Castillo de San Marcos was declared Bien de Interés Cultural in 1920, and in its interior it houses the image of the Virgin of Santa María del Puerto, which gave the city its name. It is in excellent condition, featuring spectacular courtyards and tall towers that provide beautiful views of the city.

Today, Castillo de San Marcos belongs to Bodegas Caballero, an ancient wine cellar which dates back to 1830. The winery is attached to the Castle. You can visit it to learn more about the history of Puerto de Santa María and the relevant role of wine in its story. At the end of the guided tours, it is possible to make a small tasting of the wines. The visits last about 1 hour and cost € 6.-