Geocaching is a real life treasure hunt and thousands of people are doing it across the world. The idea is to find is a small container hidden from plain site and stocked with a log book.
Cache containers come in all shapes and sizes. Some are magnetic, some look like bolts or screws, some are bigger than a shoe box. Whoever hides the cache has to record it's exact GPS coordinates and post those coordinates on a website, http://www.geocaching.com/.
The above site lists the location of all the hidden geocaching containers in the world. The coordinates listed on the site will only get the hunter within 10 feet at most of the exact location of the hidden container. So, after plugging in the coordinates to a GPS and navigating to the correct coordinates, a searcher must rely on sharp sight to find the hidden cache.
Some geocaches are big enough to hold trinkets. With these containers, cachers will take a trinket and leave one of their own. Sometimes there are "tracking coins" that are placed in geocaches. These "tracker coins" have a special code that participants can enter in on the website. In this way, a tracker coin's path can be traced from location to location. Many have been recorded to cross continents .
Anyone can geocache, and it is free. All that is needed is a GPS device (or smart phone) and a good pair of shoes.