Well, I was recently messing around with my Red Version, which I haven't done in quite a while, when I decided to pay a visit to Glitch City. I discovered another part to Glitch City, and I also (kind of) figured out the invisible walls.
OK, so for the new area,do the usual trick, using Cinnabar Island (You'll need a Pokémon that knows Surf as well as Fly). After you enter Glitch City, then keep going to left until you get stuck in an invisible wall. Make sure your trainer character is facing the right, then press your START menu, (the whole screen should be water now) and get on your Pokémon that knows Surf. Now comes the more difficult part. You'll need to navigate using your START menu. Although it looks like you're Surfing on land, press your START menu and it's actually a pond. There are 3 ponds, so you'll need to use the START button every few steps. It'll help you figure out where to go.
After you get to the 2nd pond, the whole screen should turn to water, or at least most of it will be water. Now, all you have to do is go down. Eventually you'll see those weird pillar thingys that you sometimes see in water. Just keep going down. Soon you'll find another chunk of land and houses and strange pixels, etc. I call it Glitch Island. But the only problem is that you get stuck in an invisible wall before you get to go back on land.
For those of you who have the Red or Blue Version, you might want to try it. It's really weird. The new area makes Glitch City look like the Atlantis of Pokémon games. o___o