The castalian spring is located near the ancient city of Delphi on the slopes of mount Parnassus sacred. He was revered as a sacred source of the God Apollo and the muses. According to Greek mythology, it was here that Apollo killed the dragon Python, which guarded the entrance to the Shrine, and took possession of the Oracle. Delphic temple of the Oracle was regarded as the chief centre of the worship of Apollo in ancient Greece and the most authoritative Oracle in the ancient world.

According to one version, it is believed that the name of the source has been named after the nymph Castalia, rushed to the source from pursuing her Apollo. The source provided drinking water and water for the priestesses of the oracles, the so-called pythonesses, who served this ritual ablutions before the oracles. Ancient pilgrims before you visit the Oracle in the temple of Apollo, also performed ablution in the waters of the source. According to legend, only the killers were ordered to perform ablution, while the others I could wash her hair. The waters of the castalian key is credited with medicinal properties and rejuvenating effect. Also Holy water was considered to be a source of inspiration and was particularly revered by poets and musicians.

Two keys that have fueled the castalian spring, has been preserved to our days. They were discovered during archaeological excavations in 1878 (Top Castalia) and in 1960 (lower Castalia). Lower Castalia was built around 600-590 BC near ancient road. It is a rectangular construction with a stone basin, in which water was supplied from the source through the pipe hidden under the ground. Courtyard paved with tiles and fitted with stone benches. Today this pool is clearly visible from the road. Top Castalia dated to the first century BC and built in the rock with special niches for gifts.

In modern language, the phrase "castalian spring" means a source of inspiration.