The Fort Nigtevecht is located near the municipality of Abcoude. It is one of the forts that was a part of the New Holland Waterline, and later became part of the Defence Line of Amsterdam. These lines were networks of forts and water based defences, that could be activated quickly in the event of an invasion. The Defence Line project started in 1883, and Fort Nigtevecht was the first fort from the New Holland Waterline to be linked up to the Defence Line of Amsterdam. The forts were used until the 1960s, when they were closed down. The Defence Line of Amserdam is now a national monument.