Poneglyph

Scattered among the islands of the Grand Line are mysterious stone blocks called "Poneglyphs."

About
These blocks are inscribed with the script of an ancient language, and tell of a history long forgotten. This history includes the mention of (at least) two weapons of mass destruction: Pluton and Poseidon. There are two types of Poneglyphs: the ones which carries information to reach the other Poneglyphs, which tell the True History and the ones which carries the records of True History. It has been revealed that it is against the law of the One Piece World Government to decipher them. Regardless, to reach and decipher the Rio Poneglyph is the ultimate goal of Nico Robin. It has also been revealed that Gol D. Roger was able to read poneglyphs.

Discovered Poneglyphs

 * Alabasta Poneglyph
 * Poneglyph of Shandora
 * Ohara Poneglyph
 * Rio Poneglyph