The 250 kilometre long and 4 kilometre wide wall, a military zone between North and South Korea, is famous for being the most militarised border in the world. As no people are allowed near it, an unintended side effect of the zone is that right now it is the best protected nature reserve in temperate climate in the world. On the North side, both North Korea and China designed border walls which are 1415 kilmetres long to stop the stream of refugees from the penniless North Korea. In 2006 the estimate of North Koreans refugees fleeing to China was between 20,000 and 400,000. In 2007 China began expanding the number of border control and look out points. North Korea followed by building security posts at the most popular escape routes. China then continued by increasing the height of the wall from 2.5 metres to 4 metres including barbed wire, cameras and movement sensors, to avoid an anticipated increase in refugees due to the starvation caused by a bad harvest that year. To criticism from the UN, China reacted with the explanation that the wall is intended to ‘ensure the stability of the Korean Peninsula’ and that, ‘the majority of refugees would be economic, and not political refufees’.