Write a blog article about it, but don't just provide the address and phone number, provide VERY specific instructions that one actually needs and doesn't get anywhere else, almost like turn-by-turn GPS. For example: "park by the X retail location, go inside the doors of the building under the Y sign, walk 50m just past the elevators, go up the stairs 1 level (the elevator takes forever), and you're there. You can park for free 1 block East on Y street."
I've done this for a few government offices. The earnings aren't high per month, but they have been consistent for 7 years, pretty good for an hour's work. It's doubtful the Yellow Pages, navigation providers or government website will provide such useful and detailed instructions.