According to an analysis done by Box Office Mojo, it seems Unknown's add campaign purposefully alluded to another Liam Neeson thriller: 2008's surprise sensation Taken. The tag-line for Unknown even included the word "take."
Unknown filmed on location in Berlin including the at Berlin Central Station, Oranienburger Straße, and the Hotel Adlon. The German Film Council contributed 4.65 Million Euros (about 6 Million dollars) to the film's budget.