This story is portrayed in a very light and fluffy way, but the underlying issues are pretty sad, especially when you consider the residents of the 'utopia'. It could easily be adapted into a very dark plot.
I generally like these short stories that have subliminal messages (dark with the light) without being forceful/manipulative on intended reader experience.
The story is good but it's also sad at the same time. Just thinking about the hidden city and it's residents, what are they, what happened to them, what is the hidden city really is... It's sad... And kinda dark...