According to Wikipedia, the Vinland Map is a 15th century world map drawn from a 13th century original depicting all that was known in the world at the time. A very valuable map indeed, as it depicts not only the African subcontinent and east Asia (as early as the 1200s!) but also an island labeled as “Vinland.” The island, as well as what is thought to be Greenland and Iceland, would have been information that only the Vikings new, as they were the first to areas of the new world, Newfoundland in particular.
The map was discovered, apparently bound with a series of manuscripts called Historia Tartorum, which was a description of the Tartar empire by Giovanni Carpine, which was done in the 13th century also.
Now, the map has been called a forgery, and a severe dispute has taken place in the map world. NOVA has a series on this, which you can find here. The evidences that it is a fake range from the features, some of which appear too detailed to have originated in a map drawn this early in time, the ink used and the handwriting, which is arguably 19th century, not 15th.
This kind of stuff interests us geographers, but doesn’t really dispute the evidence that Vikings were indeed in North America as early as the 11th century, as several excavations have determined that they were.
Hat tip to the Map Room.