Because Endless City doesn’t use any blocks that aren’t in vanilla minecraft, you can load Endless City worlds on accounts that don’t have the mod. And then whenever Minecraft needs a to create places you haven’t gone, it will use the vanilla minecraft world generator, leading the situations seen above. I really like the results - you can see how the Minecraft engine works by look at these boundaries, where two different kinds of generators spill over each other.
By the way, I’m maybe 65% sure that Endless City is working now, so if you’ve had trouble getting it to run please let me know. Or if you’ve successfully gotten it running, let me know also, so I can increase that probability. Or if you haven’t download it yet, why not do it now?