Only 44 kilometers or, less than an hour's drive, from Seoul, the third tunnel was discovered in October 1978. Almost identical in structure to Tunnel Ⅱ, the 1.635 kilometer-long tunnel, 1.95 meters high and 2.1 meters wide, penetrates 435 meters south of the Military Demarcation Line at a point only 4 kilometers south of the Truce Village of Panmunjom. It runs through bedrock at a depth of about 73 meters below ground. Capable of moving a full division per hour, plus their weapons, it is evidently designed for a surprise attack on Seoul. Almost identical with Tunnel Ⅱin structure, this tunnel is only 2 kilometers from a key outpost defending the Munsan corridor leaing to Seoul.