Although they look like props from an H.G. Wells film adaptation, these giant metal towers in the Thames estuary were actually constructed to protect England from German air raids during WWII. The forts were decommissioned in the 1950s, and the abandoned towers were used by pirate radio operators in the following decades. Today, one nearby fort is managed by micronation Principality of Sealand; the rest can be seen safely from a boat or, on a clear day, the shores of Shoebury East Beach.