This hermaic stele is related to one of the most important buildings of ancient Athens, the Diogeneion Gymnasium. It was found at the gymnasium΄s presumed location and is preserved intact, along with its base. The stele depicts the cosmete Sosistratos from Marathon, a mature, bearded man with short, curly hair. A two-part inscriprion engraved above and below the phallus states that the stele was erected by the ephebi in honour of their cosmete. The office of the cosmete, who was responsible for the physical and spiritual education of young men at the gymnasia, was one of the highest distinctions in ancient Greek society. The stele is precisely dated thanks to the name of the archon mentioned in the inscription.