The article presents an analysis of the idea (reflected in ancient literary sources) of Delphi as the sacral centre of Ancient Greece. The view of Delphi as the geographical centre not only of Greece, but also of the inhabited world, is a striking example of the ideal positioning of the Delphic sanctuary of Apollo in the context of the Greeks' sacral geography: it was there that they located the navel, the omphalos. This idea was a part of Delphic official ideology and was substantiated with aetiological myths supported by the Delphic priesthood and propagated by it, in particular with the aid of the poets close to the sanctuary (e.g. Pindar's odes). The myth and its interpretation were, both in early periods of the Greek history and later, not only the field of conflicts between different views and allegorical or symbolic interpretations, but also an important part of ideological propaganda and an effective weapon of political struggle in Hellas. The tradition preserved some evidence of opposition to Delphi's claims for a special role in the life of Hellas (verses ascribed to Cretan prophet Epimenides, a rival of the Delphic oracle in cathartic ritual; some mentions of omphaloi placed in other parts of Greece). The importance of Delphi as a common Hellenic centre was supplemented with its leading role in a great religious-political league, the Delphic amphictyony. Moreover, the contribution of Delphi to the idea of pan-Hellenic unity can hardly be exaggerated: Delphi may be considered as the central point of crystallization of the Greek identity. While Hellas was not united politically, common religious centres of the Greeks, with pan-Hellenic games held there, became bearers of the idea of national unity.