The Antarctic ice moves, meaning that the actual geographic "South Pole" point on top of the ice moves constantly. Every year, a team at the Amundsen–Scott South Pole Station places a new marker on what is (more or less) the current location of the pole. Of course, it's actually only accurate for about a day, as the drift rate is roughly 10 meters per year. The cool thing is, this tradition has been going on for decades, and every year a new design is created by the team who stayed over the winter prior.
(Note: Stick around for the end for discussion of the "Ceremonial South Pole," which is a little bland, but at least it doesn't move around.)