In Greek mythology, Pandora opened a pithos, a large storage jar, rather than a box.
The word pithos refers to a substantial ancient Greek container, commonly used for storing grain, wine, or oil. Hesiod used this word in Works and Days when describing the vessel given to Pandora. The familiar “box” wording arose later through a Latin translation associated with Erasmus, who rendered the Greek term as pyxis, a smaller box or chest.
This translation changed the image without changing the basic story. Pandora opened the container, releasing troubles into the human world, while Hope remained inside according to Hesiod’s account. Ancient pottery often shows pithoi as large, rounded vessels, quite unlike a modern hinged box.
The phrase “Pandora’s box” is now fixed in English and many other languages, so it is not wrong in ordinary usage. However, pithos is the more precise answer when the question concerns the original Greek object.