Walkthrough walls cheat!
But on a serious note, since glitch city is created differently dependant on where the guy tells you to get out of the safari. This means there could be about 100+ glitch city's, each with they're own amount of walk room. Since there is no record so far of the biggest glitch city (by the way, if using the walk through walls cheat to get to the "end" of glitch city it is just water. So technically you could surf as far as you wanted away from the land.) Some youtubers claim to have found big ones, I think route 6s glith city.
And a bit of a hint, don't believe the sprite terrain picture thing. They lie and some trees can be surfed on and some buildings could be cut. If you find a border, use cut and surf on the edges, you might just find another way!
