My granddad told me when he was eight living in Queens, NYC would go visit people in NYC using the subway. Eight. Alone. No problems.
When I was some young age, probably about 10, I started riding the bus to downtown Houston to watch the street life.
I learned about the winos, the legless men on their push boards, (the precursor to the skateboard), I would watch as things started unfolding for me and the patterns developed of all the under life that lives in the downtown of a major city.
I knew where the whore houses were, behind the nondescript door of the cheap hotels and learned how the elevator operators worked as front men, I watched all the wheeling and dealing of taxi drivers and businessmen and street hustlers.
As you sit on a bench for hours, invisible to the grown ups and watching, you see all kinds of things and connections, and interactions, and people pretending spontaneous contact with a stranger passing through the zone, and the little scams and all kinds of things that are not obvious at first.