Like many young boys, Denverite Chris Westerkamp once dreamed of being a pirate. Now he is—sort of—thanks to the growing popularity of geocaching, a free, GPS-enabled game in which players seek “treasure” hidden by other participants. Geocachers, whose numbers have swelled recently thanks to the ubiquity of smartphones, use coordinates and other clues to locate caches (some two million are hidden worldwide). These are usually waterproof boxes containing a logbook and, sometimes, items such as small toys. Players can take the booty only if they replace it with something of equal value. “For a lot of the caches, you have to hike, rock climb, even scuba dive,” says Westerkamp, now president of Geocaching Colorado, which promotes the sport locally. “Geocaching has taken me places I never would have gone otherwise.” Odds are, you’ve been near a cache: More than 15 are hidden in downtown Denver, nine live in City Park, and one resides atop nearly every Colorado fourteener. Create an account on and download the Groundspeak Geocaching App to get started. Exclusive: Add a treasure hunt to your next vacation with a GeoTour.