[ speaking a foreign language ] >> the villagers carved over 5,000 feet of tunnels out of the earth creating a complex that would house all 90 families of vinh moc. 13 entrances and exits leading from the inland to the beach. showing me through the labyrinth is kum tok. she since moved to the dmz to work as a guide. how did they dispose of all of this earth at rock without revealing the tunnels? >> the craters, the craters were everywhere on the landscape of the moon, and you know, the dirt of the craters are so fresh, look new, so they just left them there. >> this was the maternity ward where ton was born. >> where did people sleep? >> they have sleeping places. just like this, but smaller. two square meters only, just