This video doesn't do the tunnel any justice as it's quite impressive to walk down there in the so called "Third Infiltration Tunnel/제3땅굴". The tunnel is 73 meters below the surface, approx 1.0 mile long and quite low/narrow as you can see. Bumped my head numerous times, but luckily they provide you with helmets.
The tunnel was discovered by the South in 1978.
