Is this one of the 77 Wonders of the World ? Yes, no, vote.
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“Extending 135 km around the city of Amsterdam, this defence line (built between 1883 and 1920) is the only example of a fortification based on the principle of controlling the waters. The centre of the country was protected by a network of 45 armed forts, acting in concert with temporary flooding from polders and an intricate system of canals and locks.” More information via the World Heritage Centre.