The Crown of Athena was a piece of headware, that was sealed away in a secret location by Athena. It was worth a very high price and was hidden to prevent petty merchants and thieves from finding and selling it. The key to finding it was King Cleades, who Athena made an infant (so he could learn kindness through the eyes of a child) and then made his wife, Gryphia, an old woman (so she could learn to care). On the baby Cleades' clothing was a map that held the Crown's location.
Joxer, Meg and Autolycus found the map and subsequently found the Crown. Once baby Cleades was placed on the cushion, where he would point to the Crown, he and Gryphia would revert back to their normal age.