How do you get your mind around the universe?

Geez, it's...idk, impossible to think of something that could never end. If it does end, how would it end? Would it just be like a wall that stops you? If it is, what's on the other side of the 'wall' that stops you? Are there any theries or anything on this? I know it's meant to be like, infinite, but how could that be possible? There's walls on that little sideways 8. :S