The Defence Line of Amsterdam (Stelling van Amsterdam) is a 135 km long ring of fortifications around Amsterdam made up of forts located 10 to 15 kilometres from the city centre.
It was built between 1883 and 1920, and consisted of flooded areas (inundations) and 46 forts. All of this was dedicated to protecting the national stronghold, as an absolute final line of defence for the Kingdom of the Netherlands.