waterlines
defensive works surrounded by inundated areas
Frisian Water Line
defence line
New Dutch Waterline
Waterline in the Netherlands
Defence Line of Amsterdam
fortification line in the Netherlands
Old Dutch Waterline
waterlines in Holland, 1672-1815
West Brabant waterline
defenses in a plan to strategically flood the Netherlands
Dutch Water Line
Defensive flooding system
IJssel Line
NATO defences along IJssel river, Netherlands