Everyone seems to be looking for "Nazi gold", of course , but people are also looking for the contents of the Amber Room, which was a room in the Catherine Palace near Leningrad (now St. Petersburg), totally covered with decorative amber. This amber was removed by the Nazis, packed in a number of crates, and sent west as the German army withdrew before the Russian counteroffensive. It was sent as far as Koeningsberg, Germany (now Kaliningrad, Russian Federation), and kept in an old fortress, which was later destroyed by the Russians. Rumor has it that it was sent further west on another train before the destruction of the fortress, and that parts of this train were secreted in a Polish tunnel, the entrance of which was then blown up to cover its existence
I think that the existence of this train, or at least several boxcars of it, is more plausible than a train full of "Nazi gold", most of which is probably at the bottom of any number of eastern European lakes, if it exists at all. All of this is more plausible than the "Lost Dutchman Mine", or any number of other lost gold fantasies. 
