"It's really fun," says 6-year-old Joey Cichonski of Lindenwold, whose favorite discovery was a stretchy flamingo. "And there might be something for your parents there."
Not just treasure, either. Geocachers have a blast with everything from finding new hikes to working out mind-bending clues to tracking their traveling "bugs" around the world - and e-mailing the folks who find them. The Moyer family in Harleysville has one atop the Matterhorn right now.
As of Wednesday, at least 49,362 caches were hidden in 169 countries. In the last seven days, nearly 31,000 people have discovered these treasures and reported their finds.
The roster of players has been doubling every six months, remarkable growth for a game whose main component - hunting for treasure - has been around for millennia.
Indeed, in an era when people of all ages can spend hours immersed in online games, out of touch with other human beings, geocaching may represent the next big thing in the world of play: the convergence of the Internet with real life.
"It's a way that you can share experiences online," says Jeremy Irish, who discovered the game in its infancy and developed the site. "It's the first Internet-based sport that you can actually go out and play."
The Global Positioning System (GPS), 24 satellites built for the military, uses triangulation to calculate the position and track the movement of the GPS receiver on the ground. The Clinton administration unscrambled the signals three years ago; civilians can now pinpoint their locations to within 10 feet.
The military can get even closer. It used GPS to guide the "smart bombs" that destroyed selected sites in Baghdad.
Irish, 30, was an e-commerce developer for a failing dot-com around Bellevue, Wash., when he went on his first hunt.
"I really thought it was cool," the former Chinese linguist for the Air Force says. "I could actually use a piece of equipment, technology, to find an object in physical space."
Geocachers worldwide have adopted his philosophy: Adventure. Openness. Family. Community. "Cache in/trash out," a cute turn of phrase for cleaning up the environment.
Volunteers sign on from home to approve every treasure, screening out politics and ads in disguise. Most things on the site are free.
As the community has grown, the game and the players have diversified. Geocachers come in distinct personality types:
Hikers. The first geocachers were serious outdoorsmen and women. Most still are.
"For us, hiking is first," says Kieu Manes, 57, of Lansdale. She and her husband, Mike, known online as "Waterboy With Wife," met on a hike, had a first date on a hike, and honeymooned on a hike.
Interviewed separately, both reflected on the same favorite geocache outing: a difficult, up-and-down trek carrying heavy backpacks for eight beautiful, isolated miles along the Nova Scotia coast. Then an overnight near the cache and eight miles out.
Puzzlers. Matt Chernak (known as "CacheThis") is not really into nature. At 23, an aspiring composer of electronic music, he likes to find "weird stuff" outside. And to use his brain.
Last month, he hid his own watertight ammo box in a park near his home in Springfield, Delaware County. He called it "Numerology," because you have to solve the puzzles with numbers spied on the way.
Families. Janie Moyer figures that if not for geocaching, she'd be watching more TV. This, she believes, is better:
"My [3-year-old] brother likes it for finding the treasure. Me and my mom compete on who can find it first. And my dad likes the hiking and outdoor stuff."
At age 12, she says she's comfortable enough to use GPS to find her way out of the woods.
Sarah Wray, 7, and her sister, Harley, 5, of Penns Grove, N.J., have been tracking their six-inch stuffed animal, "The Traveling Dweebster," for 24,178 miles online.
"There are pictures of it with a girl; a dog carrying it. The kids get a big kick out of that," says Rod, their 40-year-old dad.
The travel bug moved from the United States to Panama to Australia to New Zealand, and recently hitched a ride out of a German "confluence cache" (North 51 00.000, East 013 00.000).
Techies. "I'm into the high-tech toys and stuff," says Jack Ryan, 39, a Collegeville geocacher who builds database applications for a living. Geocaching.com is his second-most favorite site, after Amazon.com.
"Everything is linked!" he says. "You click on one, it tells you all the other people that have gone there."
It also can fetch lists of treasure by latitude/longitude, state - Pennsylvania has 1,230, New Jersey 723, Delaware 55 - and country (none in Iraq but one in Kuwait, two in Israel and 69 in Saudi Arabia).
(Techie alert: Sales of handheld GPS units are booming, and prices slowly declining. Retail averages just under $300, according to industry analyst Frost & Sullivan; many geocachers say equipment costing a third as much does fine.)
Every geocacher has a piece of the different personalities. Lawrence Harty, or "The Artful Dodger," is a true multiple. A 37-year-old South African transplanted to North Jersey, Harty has buried a "JukeBox" cache that plays through your PC and proudly proclaims a worthwhile cache on the island of Bimini awaits the scuba diver who finds its coordinates, etched into a green plaque on a shipwreck 100 feet down.
Just one has tried, and failed.
More typical is the bunch of junk Len Oranzi and his 13-year-old son, Chris, discovered in a rotten tree stump two weeks ago: a Mickey Mouse trinket, two $1 bills, a button for Haddonfield's First Night celebration last New Year's.
The walk along West Deptford's sandy trails was easy, and Len's Garmin eTrex GPS - a 50th-birthday present from his wife last October - got them within 20 or 30 feet of the cache, although it took 20 minutes for Chris to spot it under the bark in the rain.
Still, they rated the outing worth the effort. They had discovered a nifty "Field of Dreams" playground, and thought they'd come back later.
"This place has cool baseball fields," Chris said, as they headed home to Wallingford.
These connections between players in the virtual world and "in real life" interest Doug Davis, a Haverford College psychology professor who has studied the cyberculture of mass role-playing games.
"I think this is going to be a growth industry," Davis says. ". . . There are people IRL [in real life], and there are people on screen."
Irish, the father of geocaching, has the same sense.
He has created a company, Groundspeak Inc., that is developing "the tool set for building location-based adventures" using technology, the Web, and the world.
The company has designated April 26 as International Cache In/Trash Out Day. It will be a test of whether a virtual community can collect real garbage (and have fun while doing it).
Contact staff writer Don Sapatkin at 610-313-8246 or firstname.lastname@example.org.
Other games that combine GPS and the Web:
www.WheresGeorge.com Track dollar bills marked "Where's George?" Input serial numbers, then spend and follow them.
confluence.org Visit latitude/longitude degree intersections, and photograph and post them online.
www.PhotoTag.com Take one picture with a "PhotoTagged" disposable camera, then pass it on. Pictures end up online.
Highpointers.org The goal is attaining the high point in each of the 50 states. The Highpointers Club fee is $15 per year.