The U.S. government warns Americans against traveling to North Korea, specifically stating that travel to the Hermit Kingdom risks "arrest and long-term detention." There have actually been many Americans held by North Korea, most were subsequently sentenced to a fine and years of hard labor. It happened most recently in January 2016, when 21-year-old Otto Warmbier was arrested for stealing a political banner from a hotel. Warmbier was sentenced to fifteen years "for crimes against the state."
(photo: Korean Central News Agency)
In addition to Warmbier, North Korea is currently holding Kim Dong-Chul, a naturalized American citizen, for espionage. He has been held for 153 days at this writing.