In 196 B.C.E., 13-year-old Ptolemy V was crowned King of Egypt. One year later, the priestly council of Memphis — an ancient Egyptian river city — commemorated the occasion (and affirmed his royal cult) by issuing a routine decree.
Their words were carved onto a granodiorite rock slab in three different scripts. Toward the bottom, the message appears in ancient Greek. Halfway up, we see it expressed in Demotic, a popular handwriting system the Egyptians had used for over a thousand years, from the seventh century B.C.E. until the fifth century C.E.
Then, up at the very top, the council's decree was written out again in an intricate, endlessly fascinating collection of symbols: Ancient Egyptian hieroglyphics.
French engineers rediscovered a large chunk of this slab in 1799 C.E. (alas, the rest has been lost to the ages). Since it turned up in Rashid, Egypt, formerly called "Rosetta," the artifact became known as the "Rosetta Stone."
Perennially, it's the most popular exhibit at the British Museum in London, England. And for good reason: The Rosetta Stone helped scholars decipher Egypt's long-mysterious hieroglyphic system.