Here's some more information:
* Old Persian was a form of the Indo-Iranian language family, related to modern languages like Farsi (Persian), Pashto, and Hindi.
* It was the official language of the Achaemenid Empire (550-330 BCE), established by Cyrus the Great.
* Old Persian was written in a cuneiform script, adapted from the Mesopotamian system.
* The most famous inscription in Old Persian is the Behistun Inscription, carved into a cliff face in modern Iran. This inscription details the history of Darius I, one of the Persian Empire's most powerful rulers.
However, it's important to note:
* While Old Persian was the official language, other languages were spoken throughout the vast empire. These included Aramaic, Elamite, and various local dialects.
* The Persian Empire itself evolved, with different languages becoming dominant over time. For instance, during the Sassanid Empire (224-651 CE), Middle Persian was the official language.
* Today, Farsi (Modern Persian) is the official language of Iran and is still closely related to Old Persian.
So, while Old Persian was the primary language of the Achaemenid Persian Empire, it was just one language spoken within its diverse population.