Believe it or not tunnels play a very important part in warfare to name just one of the issues.
I did a small look at some of the tunnels that are worldwide in scope:
its here:
https://freerepublic.com/focus/chat/4188586/posts?page=1028
post #1027
its a lot to repeat here and Im still struggling with a really bad cough.
Revelations Chapter 6
Sixth Seal: Cosmic Disturbances
12 I looked when He opened the sixth seal, and [g]behold, there was a great earthquake; and the sun became black as sackcloth of hair, and the [h]moon became like blood. 13 And the stars of heaven fell to the earth, as a fig tree drops its late figs when it is shaken by a mighty wind. 14 Then the sky receded as a scroll when it is rolled up, and every mountain and island was moved out of its place. 15 And the kings of the earth, the great men, the rich men, the commanders, the mighty men, every slave and every free man, hid themselves in the caves and in the rocks of the mountains, 16 and said to the mountains and rocks, “Fall on us and hide us from the face of Him who sits on the throne and from the wrath of the Lamb! 17 For the great day of His wrath has come, and who is able to stand?”