For the Geo Quiz, we're looking for the southern-most post office in the world. Not the one in Tierra del Fuego, at the tip of Argentina. That's not southern enough.
The one we want you to name operates in some pretty inhospitable territory. In fact, there's no mail service in the winter there but otherwise, most mail comes to this station by plane, via Christchurch, New Zealand.
So that can mean delivery delays of five to 14 days. Packages can take up to six weeks to reach this destination.
One final clue: most of the people who rely on this postal station are scientific researchers. And yes, they sell stamps there.
It's located at the Amundsen-Scott Base at the South Pole, Antarctica.
Further north, the US Postal Service is looking for fresh ideas on how to cut costs. With a multi-billion dollar budget shortfall looming, the postmaster general is already asking Congress for permission to take a number of steps. Like stopping Saturday deliveries and cutting as many 120,000 jobs.
Which got us thinking about how postal systems in other parts of the world are coping, and which ones work best. Those are good questions for an international postal expert like James Campbell. He's one of the editors of the Handbook of Worldwide Postal Reform.