Torreon Muralla Jerez The wall of Jerez de la Frontera is a construction of Andalusian origin that formerly protected the city of Jerez de la Frontera , autonomous community of Andalusia , Spain , and which currently defines the perimeter of the old town.The walls are 2.60 metres thick and 9 metres high. They are made of rammed earth, using brick and stone in some sections. The Alcázar of Jerez de la Frontera is a former Moorish alcázar, now housing a park. The first fortress was probably built in the 11th century, when Jerez was part of the small kingdom of the Taifa of Arcos de la Frontera, on a site settled since prehistoric times in the south-eastern corner of the city. In the 12th century, a new structure was erected to be used as both residence and fortress by the Almohad Caliphate. Later, after the Reconquista, it was the seat of the first Christian mayors and its development continued with a palace and other structures.