I think what this film wants to tell us was the importance of nature and how we live in the condition without nature. In the beginning of the story, the whole world was filled with full of nature and blight atmosphere. But soon after other people come, the whole nature was destroyed and filled with dark and polluted air. I thought the main character in this story is a environmentalist, and what he was doing at the first was investigating the nature. There were also some other people who seems to be environmentalists. If you look at this point, it is sarcastic in a way because you can take their investigation as preparation of making the city with lots of skyscrapers.
But in the end, the city wasn't lasted forever, and what there were left was decadence of the man-made society and leftover of strong nature power which seems to last forever.
