Castalia

Classical sources present variant accounts. One tradition reports that the Castalian Spring already existed when Apollo came to Delphi searching for Python. Another account, recorded for example by Lactantius Placidus in commentary on Statius, relates that the nymph Castalia, pursued by Apollo's amorous advances, threw herself into a fountain at Delphi (or at the base of Mount Parnassus or at Mount Helicon) and was transformed into the spring that thereafter bore her name. Apollo is later said to have consecrated the spring to the Muses (Castaliae Musae).

Literary tradition characterizes Castalia as a "young nymph" (a naiad) but supplies no sustained physical portrait; classical summaries identify her as a humanlike water-nymph rather than giving detailed bodily or dress features. Equally, the Castalian Spring is described as a sacred spring near Delphi (also variably placed at the base of Mount Parnassus or on Mount Helicon) without elaborate geographic description in the provided sources.

Sources attribute to the spring (and by extension to Castalia) the power to inspire poetic genius: "those who drank her waters or listened to their quiet sound" received poetic inspiration. The waters also had a ritual, practical function in the sanctuary: they were used to clean Delphian temples. Castalia's mythic behavior includes metamorphosis or self-immersion to escape Apollo, a common motif in nymph narratives; she is integrated into the network of river-god genealogies as a daughter of Achelous and stands in ritual relation to Apollo and the Muses.