The Rosetta Stone was found built into the wall of a fort.
In 1799, French soldiers demolishing a wall in a fort in the Nile Delta found a slab carved with the same decree in three scripts: hieroglyphs, Demotic and Greek. Because scholars could read the Greek, it became the key to a script nobody could read. Cracking it still took more than two decades.
The stone records a decree issued in 196 BC by a council of priests at Memphis, honouring the young king Ptolemy V and establishing his divine cult. It was probably first displayed in a temple, possibly at Sais, and later reused as building material. In July 1799, during Napoleon's invasion of Egypt, soldiers strengthening Fort Julien near Rosetta, modern Rashid, uncovered it, and officer Pierre-François Bouchard realised its significance. When the British defeated the French, the stone passed to them under the Capitulation of Alexandria in 1801, and it has been on display at the British Museum almost continuously since 1802. It is the most visited object there.
Its three texts say essentially the same thing. The Greek could be translated at once, and a full translation appeared in 1803. The Egyptian scripts were another matter. Scholars had long been misled by the belief that hieroglyphs were purely symbolic pictures. Key steps followed. By 1802, work by Antoine-Isaac Silvestre de Sacy and the Swedish scholar Johan David Åkerblad on the middle text had shown that Demotic spelled foreign names with sound-signs; Thomas Young found the name Ptolemy in the hieroglyphs and noticed many links between hieroglyphic and Demotic signs.
The breakthrough came from Jean-François Champollion. In 1822, using the Rosetta Stone and an obelisk from Philae that carried the names Ptolemy and Cleopatra, he worked out an alphabet of phonetic hieroglyphs, and went on to show that sound-signs were used to spell native Egyptian words too, not just foreign names. He announced his results in Paris in 1822, though reading Egyptian texts confidently took years more.
Some surprises: the stone is not basalt, as long thought, but granodiorite. Its black look came from chalk and wax applied in the museum, removed in a 1999 cleaning to reveal grey stone with a pink vein. It isn't unique either; other copies of the decree, and similar multilingual decrees, have since been found. But it came first, and its name now means any key to a new field of knowledge.
Source: Wikipedia — Rosetta Stone · Text summarised from Wikipedia (CC BY-SA 4.0)
