&gt; They come from numbers of people.<p>Huge numbers of people on medium or large areas. There is no way around it: infrastructure also means stuff like waste handling, clean energy, clean transport, etc. These huge megacities often provide the least clean and the least modern infrastructures. Take Beijing. The city has a ring of waste disposal sites around it. Many of them are fully unregulated and illegal. Basically a catastrophe in the making.<p>&gt; favour of dense cities<p>Dense cities have their own problems. They grow like cancer in the outskirts, because the dense parts growth is only in skyscrapers. The modern dense city is completely different from the small town here in Germany from the middle-ages (I grew up in one). My theory is that we have seen nothing yet. Once cities like the big ones in China will age, they will be hell on earth. Their impact on the people living their will be a nightmare. We&#x27;ve seen it in East Germany and also certain West German cities after the war. The centrally planned cities with low-quality buildings, degrading over time, at some point start to be fully depressing.<p>&gt; Only dense cities can be walkable<p>Use a bicycle.<p>I&#x27;m currently living in the outskirts of one of the bigger German cities (Hamburg). I can tell you, the quality of life is really really amazing - at least for me and my interests. This quality of life is very very hard to get in the center of the town, which btw. is only 30 minutes away with public transport.