"Chris became surprisingly introspective. 'I did examine myself,' he said. 'Solitude did increase my perception. But here's the tricky thing—when I applied my increased perception to myself, I lost my identity. With no audience, no one to perform for, I was just there. There was no need to define myself; I became irrelevant. The moon was the minute hand, the seasons the hour hand. I didn't even have a name. I never felt lonely. To put it romantically: I was completely free.'"
These words came from Christoper Knight, the man known as the Hermit of North Pond, in Maine, as quoted in a GQ article by Michael Finkel. Christopher Knight lived for 27 years by himself in the Maine woods, in a well camouflaged tent that was not discovered until he was arrested. He claimed never to have lit a fire and to have survived off food and supplies he stole from cabins and camps, where he was eventually found. The whole story is fascinating, a man who could live so long without human interaction, and how it affected his sense of self.
Plato, having asserted that no man can be entirely self-sufficient, determined though an arcane (to me) mathematical formula in (Laws), that the ideal size for a city would be 5040 people who would be ruled by guardians educated to guide the citizenry wisely.
Aristotle was looser in his estimate of the lower limit, saying (in Politics) that a city need only be large enough to be self-sufficient and that a city must not be too large to have order and strict rule of law. He felt it important that people have the ability to know one another... to select officials without personally knowing them he describes as 'haphazard'. The ideal upper limit "...the largest number which suffices for the purposes of life, and can be taken in at a single view."
There are probably urban hermits living in some old buildings or hiding out in Central Park. One cranky and clever loner finagled a multi-million dollar settlement out of a developer for finally agreeing to move out of the Mayflower Hotel so that it could be torn down to make way for a luxury condo building. Folks such as him live as alone as Christopher Knight did, but their isolation is not geographical, and in this electronic age they may not reach the kind of eccentric peace he found free of mirrors, cameras, application forms, social media; free of the glances we consciously or unconsciously respond to, or the glances that don't come, that we also respond to. Despite all the people to "perform" for, with everyone searching for reflections in their phones or the number of friends or followers or "hits" they have, the only watchers may be those who review surveillance camera footage.