The Maunsell Forts were built in the estuaries of two of England's largest rivers, the Thames and Mersey. Constructed during World War II, they housed artillery teams. Despite being decommissioned in the 1950s, the towers still stand, looking like the set of a post-apocalyptic movie or a sci-fi television show. Pirate radio stations used the forts in the 1960s as broadcast bases. Campaigns are underway to launch an official preservation effort.