The ’Inlaatsluis benoorden Fort bij Kudelstaart’ or, Inlet Sluice near the Fort at Kudelstaart is a Unesco protected monument. It was a part of the Defence Line of Amsterdam. The Sluice, and the Fort, were constructed between 1880 and 1894, as part of a much longer running project to construct a network of such forts, that would guard toe capital city. The Defence Line was later closed down, as advances in modern warfare made it obsolete.