"Stelling van Amsterdam" (military defensive line) in the Netherlands build between 1880-1914. Included by UNESCO in the list 'World Heritage Site' in 1996. This defensive line was never used and became soon obsolete after the inventation of the aeroplane.
Disclaimer: The exact location of the forts and inundation areas may differ from reality to a slight extent.
Made by Niels Bosboom.