The Behistun inscription
A trilingual cliff text that unlocked cuneiform

Darius I had a relief and an account of his accession and victories over rebels carved on a cliff by the road from Mesopotamia to Media, in Old Persian, Elamite and Babylonian. In 1835–47 Henry Rawlinson copied it, and it became the key to deciphering cuneiform, as the Rosetta Stone was for hieroglyphs.
Wikipedia (Russian) · Wikipedia (English) · 6th century BC
Meanwhile around the world (±25 years)
Europe
- c. 509 BC Founding of the Roman Republic — 11 years later
- 508 BC Cleisthenes' reforms and the birth of democracy — 12 years later
Asia
- c. 500 BC Sun Tzu's The Art of War — 20 years later
Alive at the time
- Pythagoras (aged 50)
- Gautama Buddha (aged 43)
- Confucius (aged 31)
- Darius the Great (aged 30)
- Sun Tzu (aged 24)
- Leonidas I (aged 20)
- Heraclitus (aged 15)
- Themistocles (aged 4)