The Castillo de San Sebastián is a historic fortress located in Cádiz, Spain. Built in the 18th century, it was designed to protect the city from naval attacks. The castle features a unique octagonal shape and is surrounded by water, making it a strategic defensive point. Today, the castle is a popular tourist attraction, offering stunning views of the Bay of Cádiz. Visitors can explore its well-preserved walls and learn about its history through informative displays. The site also hosts cultural events, enhancing its role as a significant landmark in the region.