The sacred spring in Delphi is known as the Kastalia Spring. It was inextricably linked to the oracle and this is where Pithia, the priests and the clerics washed, as well as the theopropi (those wishing to consult the oracle and Pithia). The water from the spring also cleansed the temple of Apollo.
The Kastalia is in the Faidriades gorge, on the rock called Flemboukos (in ancient times it was known as Iambia) and according to tradition owes its name to a nymph who fell in the spring in order to be saved from the pursuit of the love struck Apollo. The water reached the fountain located between the ancient gymnasium in Delphi and the shrine of Apollo through a pipe.
The first fountain dates back to 600-500 BC and is situated near the ancient road (it is the fountain that you can see today next to the public road). You can also see the Lower Kastalia with a basin and a courtyard with stone benches. The newer form is that of Kastalia of the Rock dating back to about the first century BC about 50 meters above the point where the old one was.