the use of aircraft rendered it obsolete after World War I. It was, however, maintained and kept in service until it was decommissioned in 1963. The dike through the Haarlemmermeer, which made it possible to flood the southern portion of the polder while the northern portion could continue to produce food for Amsterdam, is now cut by the A4 motorway. The motorway also goes under the Ringvaart at Roelofarendsveen, which makes the flooding of the Haarlemmermeer Polder and thus the future use of the Stelling no longer possible. In 1996, the complete Stelling was designated as a UNESCO World Heritage Site. List of forts North front Fort near Edam Fort near Kwadijk Fort North of Purmerend Fort along Nekkerweg Fort along Middenweg Fort along Jisperweg Fort near Spijkerboor Northwest front Fort near Marken-Binnen Fort near Krommeniedijk Fort along Den Ham Fort near Veldhuis Fort along the St. Aagtendijk Fort in the Zuidwijkermeerpolder Fort near Velsen Coastal Fort near IJmuiden West front Fort North of Spaarndam Fort South of Spaarndam Fort near Penningsveer Fort near the Liebrug Fort along the Liede Southwest front Fort near Vijfhuizen Battery along IJweg Fort near Hoofddorp Battery along Sloterweg Fort near Aalsmeer South front Fort near Kudelstaart Fort near De Kwakel Fort along the Drecht Fort near Uithoorn Fort Waver-Amstel Fort in the Waver-Botshol Fort along the Winkel Southeast front Fort near Abcoude Batteries along the Gein Fort near Nigtevecht Fort near Hinderdam Fort Uitermeer Weesp Fortress Zuiderzee front Muiden Fortress Battery near Diemerdam Fort Pampus Batterij near Durgerdam (Vuurtoreneiland) See also Dutch waterlines Old / New Dutch Waterline Grebbe line IJssel Line Maas Line Peel-Raam Line Other Defence lines of the Netherlands References External links Website of the Defence Line of Amsterdam Website about the Defence Line of Amsterdam Virtual Tour Visit site in 360° panophotography World Heritage Sites in the Netherlands Buildings and structures in North Holland 19th century in Amsterdam 20th century in Amsterdam Forts in the Netherlands Tourist attractions in North Holland National redoubts