Rio Poneglyph

The Rio Poneglyph, which contains the true history of the One Piece world (including the "Void Century" that is forbidden to be researched),is said to be found on the island of Raftel at the end of the Grand Line. Once found it will reveal the lost history from the Blank Century. According to Robin the Rio Poneglyph is the message carried by all the Poneglyphs along the Grand Line.