In short, geocaching is a high-tech, worldwide treasure hunt (geocaches can now be found in more than 180 countries) where a person hides a cache for others to find. Generally, the cache is some type of waterproof container that contains a log book and an assortment of goodies, such as lottery tickets, toys, photo books for cachers to fill with their own photos, or music recordings. Longitude and latitude coordinates are then posted on the geocaching Web site, along with a description of the cache, a hint, and any other pertinent information. Once a cache has been posted, it is ready to be discovered--and so the hunt begins!The geocaching site has a searchable database so that you can search for caches located in your area. Once you determine which cache you want to find, you have to enter the longitude and latitude coordinates into a global positioning system (GPS) unit. The unit can then be used to navigate to the location on earth (what a concept!) where the cache is hidden. Because GPS units are accurate to within several meters, the verbal descriptions are very useful in finding the cache. Often you are within inches of the cache and don?t even know it! There are several cache variations, and each has some excellent classroom applications, and this article describes 4 variations on this theme.