Ancient sources place Hyperborea variously beyond the Rhipaean Mountains, beyond the river Eridanos, or simply "beyond the north wind" — descriptions that shift according to author and era, always keeping the land just past whatever the current edge of Greek geographic knowledge happened to be. Hecataeus of Abdera devoted an entire lost treatise to Hyperborean customs; later writers describe a circular temple to Apollo at their capital, tended by priest-kings called the Boreades.
Every year, tradition held, Apollo left Delphi in autumn to winter among the Hyperboreans, returning in spring drawn by a chariot of swans — a departure and return so central to Delphic religious life that it structured the oracle's own cult calendar, with the sanctuary considered to operate under Dionysus's authority during Apollo's Hyperborean absence. The Hyperboreans, for their part, were said to send offerings wrapped in straw southward through intermediary peoples until they reached Apollo's temple on Delos.