The Cu Chi Tunnels go for miles and miles under Vietnam's surface.  There are three different levels which the Viet Cong used to out strategize US troops and Southern Vietnam forces.  

You can see me getting into one of the secret entrances that was camouflaged with leaves.  The hole was probably only a foot wide (my hips barely fit).  Once I got inside the tunnel was even smaller and soldiers would spend weeks down there!!  The tunnels consisted of larger cubbies where men would meet up and hang out for a while, eat, play cards, drink beers, you know the usual things you do underground when there is a war going on above you.  

The pictures here are of me getting in, going down, completely gone underground and then coming back up again.