"tubes" of sheet metal. After docking, we realized that they were actually 40-foot tanks from oil tankers. Through some bushes we saw the fallout shelter burrowed into the side of a mountain...Jackpot! 

We noticed there was a generator in front with fresh gas still inside. We slowly crept up to the entrance and tried to enter through the door. The door seemed to be locked from the inside. On the door there was a "peep hole" with a metal bar slid over it. While we were banging on the door and trying to pry the door open, all I could remember thinking was, “If that peep hole slides open and I see a crazy hillbilly, I'm not going to need the canoe, because I'm going to run over the top of the river to get back home.

We searched all around and found out that there were actually several tankers welded together. There were a few more entrances, but all the doors were locked. We climbed to the top of the shelter and discovered manhole covers that were also welded in, but could not be popped open.