Geocaching is an outdoor treasure-hunting game in which the participants use a Global Positioning System (GPS) receiver or other navigational techniques to hide and seek containers (called "geocaches" or "caches") anywhere in the world. A typical cache is a small waterproof container containing a logbook and "treasure," usually toys or trinkets of little value. Today, well over 440,000 geocaches are registered on various websites devoted to the sport. Geocaches are currently placed in 222 countries around the world and on all seven continents, including Antarctica.