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Some enthusiasts hide boxes in urban areas. (There's one near the Lincoln Memorial in Washington.) But in this day and age, such sites present a unique set of problems. "If you're hiding one in a city somewhere, or near a bridge or something that might be a target for terrorists," says Carpenter, "it definitely is a concern." To lessen anxiety, most boxers use translucent containers so that people can see inside and know they're safe. Ultimately, however, the game is about the thrill of the unknown. In April the Connollys found themselves in the middle of a herd of wild boar near Tampa, Fla. Says Lori: "If not for letterboxing, we never would have seen something like that."