The Holland Water Line was a series of water based defences conceived by Maurice of Nassau in the early 17th century, and realised by his half brother Frederick Henry. Combined with natural bodies of water, it could be used to transform Holland, later together with Utrecht, almost into an island.
Today many of the forts are still more or less intact. There is renewed interest in the waterline for its natural beauty. Bike tours and hiking paths are organised with the line as theme. Some of the forts are open for bikers/hikers to stay the night. Others have a variety of uses, for example Utrecht University houses its botanical garden in Fort Hoofddijk.
Due to the unique nature of the line, the Dutch government is considering whether to nominate the whole defensive line as a UNESCOworld heritage site, as they did with the ring of fortresses around Amsterdam.
A twenty-five year plan has been developed by the artist, Agnes Denes.
In 2010, one of the forts on the Line, Bunker 599, was opened as a publicly accessible work of art. The bunker was sliced open, with a walkway placed through it forming an installation allowing a view to look into and through the bunker.