There were these ancient Ukranian mega cities 6-4k years ago that stood for thousands of years. They had gardens, and what appeared to be a complex social life. Notably, they had no walls, meaning there was nothing to protect themselves from. Peace.

So yeah, there sounds a lot better. No walls to stop friends from coming, or you from leaving if you happen to not like it.

Just because we lack imagination doesn't mean a better world can't exist and didn't exist somewhere in the past.