The Rosetta Stone

The Rosetta Stone is an ancient Egyptian artifact that dates back to the Ptolemaic era. The stone is a stele with 3 different translations of Ptolemy IV's Decree of Memphis in 218 BC, translated in hieroglyphic, demotic, and classical Greek. The stone was found in 1799 by the French in the Egyptian city of Rosetta, and drastically helped anthropologists to decipher Egyptian and Hieroglyphic writing, which was understood little before the 1800s.

Story of the Rosetta Stone from http://www.ancientegypt.co.uk/writing/rosetta.html