It looks like you people stumbled on a Deep Underground Miltary Base known as D.U.M.S...
There are 146 Bases throughout America and many subterrainian tunnels leading upto Universities. You aquired level 1 , this is where the transit and parking lots are and trains for the tube shuttles. Lucky you did not make it any farther.
They have orders to shoot to kill people with no badges. That tunnel links up with the tunnel network and goes down 4 and one half miles .
Over 20 levels. You made it to level one. Thanks for the pictures. I was hoping someone would have got a closeup picture of a Tube shuttle. Those fuckers can do Mach 2.7