Ueno is an interesting little district in central Tokyo. Famous for its zoo, park, museums, and shitamachi 「下町 」– lit. the "low city".
Shitamachi contrasts with the upper-class yamanote (foothills), though the two regions have always been vaguely defined, as their identity was more based on culture and caste than on geography.
I actually walk through Ueno most evenings, on my way home from work. I'm often asked by touts if I would like to make use of their services (I'll leave the various offers to your imagination), as I briskly walk through the area.
It's kind of strange, because it's one of the seediest areas in Tokyo, and though there is a variety of such establishments, there are some rather nice looking restaurants and bars, and the whole area is still an extremely safe place to be...