The 3rd Tunnel was discovered by South Korea in 1978. It spans over 1,635m in length, 2m in x_width, and 2m in x_height and is located 52km from Seoul. It is estimated that approximately 30,000 soldiers could move through the tunnel per hour. The scale is similar to the 2nd Tunnel, but it was thought to be more threatening as an invasion tool than the 1st and 2nd Tunnels. Located only 4km away from Imjingak toward the southwest and 3.5km from the Tongilchon area, it is accessible by car in approximately 45 min from Seoul.