Geocaching is using GPS coordinates to find an item hidden by someone else. They vary in size from very small to the size of a gallon jug (or even bigger), and usually contain a log that finders can sign. If you're interested - check out the geocaching links on the right of the page for more info and how to find them!
If you're coming to Hartman Creek to geocache, you're in luck - there are a lot! As of early 2019, there are over 50 geocaches in the park. There are several individual ones, as well as series that lead to a final solve. There are even more hidden along the Ice Age Trail and in Emmons Creek Nature Area south of the park. And if you're making a day or more of it, look around the Waupaca area too - all together there are over 500 geocaches in the Waupaca-area.