[The World's 20 Most Amazing Tunnels]North Korean Infiltration Tunnels, DMZ

 

 

 

Starting in the 1970s and continuing through the 1990s, U.S. and South Korean military stationed along the 160-mile-long Korean Demilitarized Zone began discovering a series of tunnels dug by North Korea for incursion into the South. Four have been discovered; many more may lie below the surface. (Eric Wishart/AFP/Getty Images)