Seville was first fortified in 1135 under Almoravid sovereignty. By the thirteenth century, they had been reinforced and expanded upon until they extended up to six kilometers complete with 116 towers and twelve city gates. In the 1860s however, the great walls were razed to afford municipal growth and development. Today, only the portion between the Cordoba and Macarena gateway still stands. Constructed in rubble and debris cemented together, these walls feature seven restored towers, including the polygonal-shaped Torre Blanca and the dodecagonal Torre del Oro (Tower of Gold) part of which dates to the thirteenth century. Once a main surveillance station important for protecting the city, today the Torre del Oro serves as a naval museum.