People who don't live in cities often talk about how impersonal they are. So many people crammed into so little space. People who don't know their neighbors, even in an apartment building. People who bump and grind on the streets and subways but don't really know others very well. However, that's not how it is everywhere.
Even in New York City, communities develop in apartment buildings, work places, and through activities in buildings, parks and even in private living spaces. A doorman becomes part of a community in the building where he is employed (there are probably some doorwoman - I just haven't met one). They're usually remembered around the holidays with a small gift, monetary or otherwise. Sometimes tenants do special acts of kindness for their doorman - a cup of coffee for the late night man, maybe some tickets to something (albeit to something no one else is available to see).
Even in place as large as Central Park, with as many people who stroll through there each day, week, and month, there are sports leagues and other activities that bring people together. At the public library, there are classes and events. Behind the main library on Fifth Avenue is Bryant Park, another place of activity during the week.
People do get to know other people in cities. When there is an emergency, there is remarkable cooperation among residents. Every day, city life is vibrant, and not only with busy people hurrying to their next appointment. There are also people who stop, chat, and take a genuine interest in others.
Impersonal cities? Sometimes, but if you dig deeper, you can see people connecting, people helping others, people who do know their neighbors, their doorman, the man at the paper stand, the woman at the deli, and the woman at the grocery store. The teeming life of a great metropolis includes many friendships that go much deeper than some who've never spent much time in a city would ever imagine.