Archimedes was an ancient Greek demigod, a son of Hephaestus. He is credited with the creation of many modern machines as well as an accurate approximation of pi. He is, in modern times, considered as one of the most well-known and one of the greatest of Hephaestus' children. It is the wish among many of Archimedes' modern-day siblings to find the lost works of Archimedes. The king spared him but, he was killed by a Roman guard.
While searching for Nico di Angelo with Frank Zhang and Hazel Levesque in Rome, Leo Valdez recovered the lost works of Archimedes. He uses them to destroy the eidolons, possessive spirits working for the Earth goddess, Gaea. He planned to take them to Bunker 9 at Camp Half-Blood, to study them further. With Archimedes' works, Leo hoped to save Camp Half-Blood from the Roman forces at Camp Jupiter.
- Archimedes seems to be to the children of Hephaestus what Daedalus was to the children of Athena.
- Archimedes was a real Greek physicist, inventor, engineer, and astronomer who was killed by a Roman soldier against the orders of his superiors.
- He is mentioned in another Rick Riordan series, The 39 Clues second series.
- He was the inventor of the world's first analog computer; the Antikythera Mechanism.