Line in the tunnel with three concrete barricades. Tourists can walk as far as the third barricade, and the second barricade is visible through a small window in the third. See also North Korean infiltration tunnels Korean People's Army List of tunnels in North Korea References External links Korean Demilitarized Zone Tunnel warfare Tunnels in North Korea Tunnels in South Korea 1978 in North Korea 1978 in South Korea Espionage North Korea–South Korea relations