Geocaching—it’s a thing. In 2000, the world’s first documented geocache showed up in Beavercreek, Oregon, as a black bucket filled with random items. Since then, enthusiasts have created more than 3 million geocaches all over the world. The game is simple: seekers use GPS devices or apps to root out objects or containers concealed at specific geographical coordinates. Basically: a low-tech global scavenger hunt with much walking. We asked Lee Ann Moyer, an avid Portland geocacher, what’s up with this geeky hobby.

So let’s start at the beginning. How does geocaching work?

The app gives you coordinates and information about the cache you’re looking for: how big it is (a nanocache can be the size of a pencil eraser), how difficult it is to find (some are very complicated and tricky), and a terrain rating (for example, is it urban or wheelchair accessible?). When you find the cache, you sign the paper inside and record it online, notifying the world (and owner) that you’ve found it. You’re also not supposed to “betray” the cache. People who don’t know about geocaching are called “muggles,” and you’re not supposed to let muggles know when you’re looking for a cache.

What got you hooked?

You’re kind of wandering with purpose. It doesn’t matter really if you find the cache or not. But it gives you a small project. It feels like you’re discovering something that no one else knows about.

What are some of your most memorable finds?

There’s something you can put in a cache called a “travel bug”—a little keychain. You take it out, hold on to it, and then drop it off in another cache. We picked up a travel bug in Oregon and took it with us to Alaska. It had already been all over Europe, Africa, Spain, New York, and then Mexico. We dropped it in a cache in Juneau. A few days later, we met an older couple in the woods. We realized they had picked up my travel bug the day before. They planned to drop it off in Norway.

Is there a “typical” geocacher?

Anyone nerdy enough to think that this is super cool is probably the person who would like to geocache. One time my sister met a guy who said he had lost 15 pounds geocaching just by walking around. It gets people out.