50 Archeological Mysteries That Remain Unanswered Even Today

Ulfberht Viking Swords

The mystery that still baffles the researchers is the process used in making them, which was almost discovered 8 centuries later. The secret recipe used in making these swords was adding an adequate amount of carbon in steel and removing impurities from them by heating them at 3000 degrees Fahrenheit, a process which was not discovered till then.