In 1220, Abu Eola, the governor of the occupying al-Andalus, ordered the construction of this watchtower as part of the city walls. To further protect Sevilla from invasion, a chain was stretched across the Guadalquivir River to La Torre del Oro, thus blocking entry by enemy ships. Since 1936, the Tower of Gold has been Museo Naval. The museum has a modest collection of maritime items ranging from the Spanish navigators to military and industrial shipping.