The Access-Bridge on the Rijnlanderweg over the Achterkanaal is a part of the defensive line which has protected the Netherlands since the end of the 19th century. The defence line is made up of an intricate system of canals and locks which route water around the country, and serve to flood certain access-ways in times of war – preventing the enemy from using them. The defence lines are UNESCO protected monuments which are a testament to the ingenuity of Dutch engineers.