The Tokyo Sky City vision (it's in the design phase now with no plans for construction yet) looks to me like the designers are trying hard to come up with helpful solutions to overcrowding and resource management, and I get why they're thinking along these lines - it's very creative and solution-oriented. Building up rather than out has a lot of advantages when it comes to creating less carbon emissions, and urban density has a lot going for it in the realm of sustainability, though I understand the impetus behind this project is land pricing. However, this idea of the Sky City looks to me like one big security fail. Any skyscraper of course bears the burden of emergency preparedness, but I can't imagine what would happen to the people in a building that fits a whole city of 100,000 people in the event of tragedy. Perhaps I have more to learn about this design concept, but my gut reaction is that I'd never want to live there. If I'm being honest, though, I'd love to visit if this plan ever becomes reality.