Geocaching, the latest outdoor adventure game, promises loot at the end of a day's play. Using a Global Positioning System (GPS) unit, players search for a "cache," a weatherproof container filled with small trinkets and a logbook for the finder to sign and date. In order to keep the game going, players must replace the treasure they find with a cache of their own. Coordinates to some 36,000 caches hidden in 151 countries (more than 1,200 of them in New York City alone) can be found on www.geocaching.com. Utah's Red Mountain Spa (800/407-3002; www.redmountainspa.com; $50 per person) offers five-hour introductory classes.