George Hornberger and his 9-year-old son Duke have crawled through tunnels, paddled a canoe and waded in creeks, all the while holding a GPS that contains the precise coordinates of their target destination.

This isn't a scene from Indiana Jones. The Hornbergers aren't hunting for the holy grail, or even anything of value. They're one of thousands of families in the area who spend their free time on a high-tech treasure hunt called geocaching.

For the uninitiated, geocaching is an activity where people hide and find “caches,” or plastic containers hidden anywhere from an urban park to a hiking trail. The person who hides the cache logs onto the website geocaching.com and leaves the container's GPS coordinates—or sometimes just hints of where to find the cache—and then other users head out in search of the container. Some caches are tiny (the size of a film canister) and contain just a logbook for the finder to sign, and others are the size of large plastic Tupperware—those usually contain trinkets for the finder to trade.

Hornberger and his three kids, ages 3, 6 and 9, have discovered thousands of geocaches everywhere from a local park's playground to Pohick Bay. It's a great activity to get kids interested in the outdoors, he says, especially since you can filter your search to include only kid-friendly or easy caches.

“We like the outdoors, and we like to hike and visit new places, so this is perfect,” he says. “... We kind of mix it in with other things. We go out and find a cache, then have a picnic or visit a creek nearby.”

Geocaching dates back to May 2000, when the government removed selective availability from GPS technology, allowing anyone to precisely pinpoint a location. With this newly improved technology, it didn't take long for GPS enthusiast Dave Ulmer to test the accuracy of a set of coordinates by hiding a container full of prizes in the woods. The experiment took off, and soon others started “stashing” containers. The activity took on the name geocaching—geo, meaning Earth, and cache, meaning a hiding place.

Kid-Friendly Geocaching

Local parents say geocaching is the perfect way to get children as young as 3 off the couch and into the great outdoors, and there's a definite educational value to the hunt, too.

Kids will learn to navigate a path using a GPS map, and they'll quickly find that the direct route is not always the best route; they'll navigate around creeks, streams and thorn bushes when trying to reach their final destination.

Geocaching also encourages children to explore local parks, forests and trails. Clark Oliver, a father of three from Ashton, says he loves introducing his children to nearby outdoor destinations such as the Rachel Carson Greenway Trail in Montgomery County. While they're out, they explore the streams, turning over the rocks to look for crayfish. For suburban parents, geocaching is a reminder that the D.C. metropolitan area still has plenty of open space ripe for exploration.

“We see Kentlands and other big developments, where there are these enormous houses on tiny lots,” he says. “There's no room for the kids to play. This gets them out into the woods, and yeah, there's poison ivy and deer ticks, but you just can't beat running around in the woods as a kid. … Get outside and breathe some fresh air. Get some dirt under your fingernails and some mud on your shoes.”

Getting Started

Starting out is as simple as logging onto geocaching.com and typing in your address or the name of a local park, trail or other location.

Once you get your list of results, you may be surprised to see how many caches are located within just a mile of your location. Take a look through the results for caches ranked low in difficulty and terrain. There is also a “kid-friendly” teddy bear icon on some caches to clue parents into caches that may be better for young children.

Each listing also includes a description of the cache: its size, what's inside, hints on parking and other helpful pointers. Beneath the description, you can see comments left by others who have found that cache. Parents should read through the comments, as many people will say whether they went with their child or if there were any issues reaching the location.

Another option for finding kid-friendly locations is looking for caches placed along Ranger Rick's Geocache Trails, a partnership between geocaching.com and the National Wildlife Federation (NWF). The program uses characters from Ranger Rick magazine to get kids interested in the environment. Participating park rangers and other environmentalists hide kid-friendly caches that contain a clue card and a stamp of one of the characters. Kids who find the cache can stamp their passport (found on the Ranger Rick's Geocache Trails site), help solve a “mystery” and follow the “More to Explore” suggestions for activities to do while outdoors.

“The game cards are designed to add an educational twist, and they keep it really fun so the kids don't even know that they're learning,” says Lindsay Legendre, marketing manager for the NWF's Be Out There movement.

Once you decide on a cache to track down, it's a matter of deciding on a GPS unit. Many geocachers simply use their cell phones, either through Google Maps or a geocaching app. Geocaching.com has an iPhone app, and Hornberger recommends c:geo for Droid phone users. If you're concerned with cell phone reception in less urban areas, consider investing in a standalone GPS; Amazon.com and most sporting goods stores have GPS units recommended for geocaching.

Before you head out, be sure to take a class at a local nature center or at the very least familiarize yourself with the rules of geocaching (see sidebar for a few rules). It's important to know proper conduct before going out to preserve the quality of the game.

The real fun starts when you're on the trail, says Lisa Droubi, a park naturalist with Meadowside Nature Center who leads geocaching programs for children.

“Kids enjoy the chance to hunt something down, and then when they get close to it, they have to put the GPS down and use their eyes and start looking around,” she says. “There are ones that are just an Easter egg; it's so unexpected, or it might be a pulley system up in a tree, and you may not notice it right away. … Plus, it also gets you outdoors, and there are just so many things to see along the way.”