About Stelling van Amsterdam
Fortifications, Historic, Interesting Places, Other Fortifications
The UNESCO World Heritage Site known as the Defence Line of Amsterdam (in Dutch named Stelling van Amsterdam, pronounced [ˌstɛlɪŋ vɑn ˌɑmstərˈdɑm]) is a 135 km ring of fortifications around Amsterdam. It has 42 forts that are 10-15 km from the centre and lowlands, which can easily be flooded in time of war. The flooding was designed to give a depth of about 30 cm, too little for boats to cross. Any buildings within 1 km of the line had to be made of wood so that they could be burnt and the obstruction removed.
Source From:
Wikipedia
9, Provincialeweg, Alkmaar, Noord-Holland, Nederland, 1536AC