Geocaching is an activity where participants use a GPS or other navigating tools to track down containers known as "caches" anywhere in the world. Some caches are small and contain a log, but others are larger and contain trinkets. Caches are currently located in over 100 countries and on seven continents.
http://www.geocaching.com/
There is a type of geocaching known as "earthcaching" in which the participant has to perform a task to find the cache that teaches him or her a lesson about the science of the area.
