In this article the ancient musical ratios, that is the musi¬cal fractions still alive in the musical tradition of Greece, the Balkans and Eastern Mediterranean, are related to the geographical data of ancient sites. Thus, the musical intervallic constants also form geographical con¬stants and represent the marginal relation between day and night during the summer solstice, which was determining the geographical latitude of each location. For example, for Babylon this relation was 3/2 (three parts day and two parts night during the solstice of June 21st), for Cyzicus 5/3 (15 hours day and 9 hours night), while for Alexandria it was 7/5 (14 hours day and 10 hours night). Furthermore, it is quite probable that already since the second millennium B.C. it was known the ratio of the perfect “fourth” 4/3, which represents the geographical latitude of the Egyptian Thebes. The ratio between day and night for Delphi, having a geographical latitude 38o 35′, coincides with the har¬monic ratio of the golden mean, which justifies the name of the site “omphalos”. In Delphi the duration of day on June 21st is 14 hours and 50′ and that of night 9 hours and 10′. This ratio, which also represents the symbolism Apollo-Dionysus, is the golden ratio (1,61808…). An analogous interpretation can be applied to the meridian of important ancient sites, on the basis of the difference of sunrise and sunset in two locations. In this way the position of Delphi in the omphalos of Europe is warranted, since its location is in reality the golden mean of the solar distance between the Atlantic of the Hesperides and Atlas and the Caucasus of Prometheus.