The Netherlands is a flat country. There are no mountains or rocks suitable for climbing. They had to find a way out. Their climbing tower Excalibur is the highest climbing wall in the world - 37 meters. By the way, the photos from the air were taken by a camera suspended on a kite.
and this as well:
http://www.stumbleupon.com/su/5kM4Sb/www.inhabitat.com/2009/05/07/abandoned-silos-transformed-into-a-climbing-gym/