Another important and influential landmark in Seville, the Torre del Oro (Golden Tower) is a twelve-sided polygon that started out life as a muslim military watchtower, but it is the flag of Spain that flies from its viewpoint today. Built in the 13th century, it also served as a prison for a while, although we’d rather not think about that. It is now home to a maritime museum and a watchtower, along with the ghosts of the lost souls who came to their demise here. Maybe.