New Dutch Waterline

map of the new dutch water line areas to be inundated to protect holland

The Nieuwe Hollandse Waterlinie is an 85 kilometer long defence line with 45 forts, water sluices and two castles. It starts at the former Zuiderzee and ends at the Rhine river.
It was in use from 1870 to 1945, but its history goes back much further back in history.
Since 2021, the waterline has been on the UNESCO World Heritage List.
It is one of the few examples in the world where water is used as a defence. Inundating large areas of land made it difficult for the enemy to reach the cities.
The main parts of the New Dutch Waterline are: Muiderslot castle, Weesp fortification, Naarden fortification, island Pampus, Nieuwersluis fortress, Loevenstein castle.

https://www.theheartofholland.com/en/region/nieuwe-hollandse-waterlinie