ok, if you want to see the "UNDERBELLY" of Subay Town ( off the map ` kind of like the borderlands map glitch ), you can!
But be warned, you will need to reload your game as i have not found a way back to the main game yet.
this is all you need to do:
find the lift that take to up and down in the garage of subway town that takes you to Captain Marshall ( the car lift one) as you go down the lift try to walk off it - just try to walk off it as soon as it starts going down. if done correctly, you will fall a bit into a black area, if you look up, you can see the entire town.
I never noticed any secret ares doing this, AS i forgot to look.......
I don't know if you have used the scope pistol glitch? When you use your pistol and have the scope zoom in LT on an object in the distance, spam A button while zooming in & out you can pick up ammo collectibles from across the distance of the scope lol.
It takes a few try's to get used to it, can be handy if you want to grab stuff in a room full of mutants or hard to reach spots!