In this week's On the Town, Rosie and Li discuss a very old, big, grey stone.
The Rosetta Stone might not be much to look at, but it has a fascinating history.
It was made in 196 BC in Ancient Egypt.
The text on the stone is written in three ancient languages.
It has helped scholars to understand the Ancient Egyptian writing system of hieroglyphs.
Listen to the programme to hear the director of the British Museum, Neil MacGregor, talking about one of the most famous objects in London's British Museum.