The New Dutch Waterline is a large-scale military defence system designed in 1815 by order of King Willem I,
consisting of 60 fortresses, 5 fortified towns and over 1500 smaller waterworks, all located in the central part of the country.
The concept of controlled inundation originates from the 12th century but during the Second World War the concept of a waterline
as a defensive device proved to be useless and was abandoned, leaving an extensive ensemble of cultural and natural heritage behind.

Starting in Amsterdam, you could ride the 85 km's in 2 days but that wouldn't do justice to it's grandeur.
Better would be 3 days, or even 4 days if you visit Amsterdam castle and Loevestijn castle. The old fortresses all have different purposes nowadays:
brewery, bed & breakfast, nature, art, restaurant, to name a few. There even are fortresses where you can pitch your tent.