“Come to me, O Paean, and bring with you the true oracle,” reads the inscriptions in an oracle well used to communicate with the Olympian god Apollo that was recently discovered in Athens. Dating back at least 1,800 years, the oracle well would have been used for hydromancy, a method of divination by means of interpreting movements in water.

Jutta Stroszeck, with the German Archaeological Institute at Athens, discovered the well during an excavation in Kerameikos, a neighborhood just northwest of the Acropolis. The report on the discovery was first published by the German Archaeological Institute in 2015 but was only recently brought to broader attention by Haaretz.

The surrounding site has been under excavation since the 19th century, when archaeologists uncovered a sanctuary in Kerameikos covering some 6,500 square feet. An altar in the sanctuary venerated the goddess Artemis Soteira (“She who saves”) and her twin, Apollon Paian (“He who helps”). Near the altar was a marble omphalos, a conical stone symbolizing the navel of the world. In Greek mythology, Zeus sent two eagles flying around the globe to meet at its center, or “navel”; omphalos stones were planted near the mythical sites where they met, including, most famously, Delphi.

It wasn’t until cleaning the omphalos at Kerameikos in 2012 that archaeologists realized it had been mounted on a slab of marble, which covered a circular opening. A crane removed the omphalos, which turned out to serve as a fancy lid for a well beneath it, nearly 30 feet deep.

The walls of the well, made of clay cylinders, are inscribed with 20 repetitions of the same phrase in Ancient Greek, “ΕΛΘΕ ΜΟΙ Ω ΠΑΙΑΝ ΦΕΡΩΝ ΤΟ ΜΑΝΤEΙΟΝ ΑΛΗΘΕΣ” (or, “Come to me, O Paean, and bring with you the true oracle”). In this context, “Paean” is a nickname for the Olympian deity Apollo, son of Zeus and Leto, recognized as the god of music, truth, prophecy, healing, the sun, plague, and poetry, among other things. According to Stroszeck, this is the first oracle well discovered in Athens devoted specifically to Apollo. (The most famous oracular site devoted to Apollo is at Delphi.) Ancients would have used the oracle to seek guidance from Apollo in matters ranging from health and love to divining the future based on “messages” in the movements of the well’s water.