I decided over a decade ago to walk every street in San Francisco, every block. I'm perhaps 20% done with the project—there is a whole lot of this city outside the downtown/Mission/Hayes Valley area—but that's fine; watching the city change over the years is also part of the pleasure.
This project has, of course, made me interested in other people doing similar adventures.
Larry Burgheimer says he did all of San Francisco between 1967 and 1972 (see the second letter on this page).
Mike at Satan's Laundromat rode the entire New York subway system.
Matt Green is still working on his project of walking every street in every borough of New York City.
My latest favorites are Jo Hunt, Mary Rees, and Linda Smither who are riding every London bus route.
Hooray for wild projects!