Years ago, I got curious about a thought, why Mumbai (being my favourite cities) is a land of opportunities and dreams. 

One of the conclusions of my random thoughts was that because it is so dense with millions of people around, no one can starve really if one provides some kind of value, even if that's to sell a thing as small as a Vada Pav. 

As the cities are now growing vertically, at a single point, as a service provider/ product seller, you will have masses to pitch and sell your services to. That would result in potentially huge influx of revenue and the pursuit of your entrepreneurial journey would get a wind and direction. 

What do you think could be other reasons for dense cities to flourish more?