The significant archaeological discovery in the 19th century that provided insight into ancient Egyptian civilization was the Rosetta Stone. Discovered in 1799 during Napoleon's campaign in Egypt, this granodiorite stone slab features inscriptions in three scripts: hieroglyphics, Demotic, and Ancient Greek. The Rosetta Stone became crucial to deciphering Egyptian hieroglyphs, as the Greek inscription served as a key to understanding the other two languages. Jean-François Champollion famously translated the hieroglyphs in the 1820s, revealing the complex history and culture of ancient Egypt. The Rosetta Stone remains an iconic artifact, symbolizing the breakthrough in understanding ancient languages and civilizations.