Geocaching is an adventure game using a Global Positioning System (GPS) to find caches hidden around the world. Go to www.geocaching.com to find locations of caches in the area and rules for playing. Geocaching enthusiasts hide caches and post them on the Internet. Others then try to find them. Caches often contain a log book and rewards, according to the Web site. The general rule for participants is to leave a new reward in the cache if they take one, according to the rules. There are hundreds of caches hidden within 30 miles of Strasburg.