Now that Pokémon Go's swept the nation into a frenzied dash to Catch 'em All™, it's less a question of "Are you playing Pokémon?" and more, "Holy crap, where did you find a Scyther?" If that weren't enough, the recent confirmation that legendary Pokémon like Zapdos and Articuno are hidden somewhere in the game has given people even more reason to walk blindly into traffic/graveyards.
Unfortunately, there's really no easy way of figuring out where the rarer Pokémon will spawn in the game, short of compiling a list with every known sighting thus far -- which is exactly what one NYC Facebook group has done.
By crowdsourcing information on rare Pokémon sightings from its members, Pokemon Go NYC has compiled a database of firsthand accounts including location, borough, and time of day. Of course, since they're crowdsourced, these sightings range from the helpfully specific (90th & 5th) to the woefully broad (Upper East Side).