I heard of these forts about 2 years ago, but until recently, I couldn't remember how they were called.
I consider them fascinating mostly because they are abandoned, but almost unreachable. The kind of explore I will probably never have the opportunity to do. The internet has plenty of pics and info on the forts, and almost every urbex addict knows of their existence by now, but that didn't stop me from showing them to you once more.
The Maunsell Forts were small fortified towers built in the Thames and Mersey estuaries during the Second World War to help defend the United Kingdom. They were named after their designer, Guy Maunsell. The forts were decommissioned in the late 1950s and later used for other activities. One became the Principality of Sealand; boats visit the remaining forts occasionally, and a consortium called Project Redsands is planning to conserve the fort situated at Redsand.