In classical Greece, Lerna[1] (Greek: Λέρνα or Λέρνη) was a region of springs and a former lake located in the municipality of the same name, near the east coast of the Peloponnesus, south of Argos.

[2] Its site near the village Mili at the Argolic Gulf is most famous as the lair of the Lernaean Hydra, the chthonic many-headed water snake, a creature of great antiquity when Heracles killed it, as the second of his labors.

[4]Lerna was one of the entrances to the Underworld, and the ancient Lernaean Mysteries, sacred to Demeter, were celebrated there, along with a festival called the Lernaea, which was also held in her honor.

The water of the lake is, to all appearance, calm and quiet but, although it is such to look at, every swimmer who ventures to cross it is dragged down, sucked into the depths, and swept away.

[5]At Lerna, Plutarch knew (Isis and Osiris), Dionysus was summoned as "Bugenes", "son of the Bull" with a strange archaic trumpet called a salpinx, while a lamb was cast into the waters as an offering for the "Keeper of the Gate."

[12] The burning of the House of Tiles brought the Third Period at Lerna to a decisive close; a low round tumulus marked its undisturbed, apparently sacrosanct site.

A great profusion of unlined pits (bothroi) was characteristic of this phase: eventually they became filled with waste matter, bones, potsherds, even whole pots.

Modern geological techniques such as core drilling have identified the site of the vanished sacred Lake Lerna, which was a freshwater lagoon, separated by barrier dunes from the Aegean.

Deforestation increased the rate of silt deposits and the lake became a malarial marsh, of which the last remnants were drained in the nineteenth century.