Castalian source is located near the ancient city of Delphi on the slopes of sacred Mount Parnassus. He was revered as a sacred source of the god Apollo and the Muses. According to Greek mythology, this is where Apollo killed the dragon Python who guarded the entrance to the sanctuary, and took possession of the oracle. Delphic temple of the oracle was considered the main center of worship of Apollo in ancient Greece and most authoritative oracle in the ancient world.

According to one theory it is believed that the source of its name was named after the nymph Castalia, threw herself into the source of her chasing Apollo. The source provided drinking water and water for the priestesses, oracles, the so-called pythonesses who are committed ritual ablutions before the oracle. The ancient pilgrims, before you visit the oracle in the temple of Apollo, also bathe in the waters of the source. According to legend, only the killers were ordered to perform ablution, while others could only wash your hair. Waters Castalian key ascribe healing properties and rejuvenating effect. Also sacred waters were considered a source of inspiration and most revered poets and musicians.

Two keys that feed Castalian Spring, survived. They were discovered during archaeological excavations in 1878 (Upper Castalia) and in 1960 (Lower Castalia). Lower Castalia was built around 600-590 years. BC. next to the old road. It is a rectangular structure with a stone basin in which the water comes from a source through a pipe hidden under the ground. The courtyard is paved with stone tiles and equipped with benches. Today, the swimming pool is easily visible from the road. Upper Castalia dates from the first century BC. e. and built into the rock with special niches for gifts.

In today's language, the phrase "Castalian source" means a source of inspiration.