Lerna Heracles killed it, as the second of his labors. The strong Karstic springs remained; the lake, diminished to a silt lagoon by the 19th century, has vanished. Lerna is notable for several archaeological sites, including an Early Bronze Age structure known as House of the Tiles, dating to the Early Helladic period II (2500–2300 BC). The secret of the Lernaean spring was the gift of Poseidon when he lay with the "blameless" daughter of Danaus, Amymone. The geographer Strabo attests that the Lernaean waters were considered healing: Lake Lerna, the scene of the story of the Hydra, lies in Argeia
Lerna a "salpinx," while a lamb was cast into the waters as an offering for the "Keeper of the Gate." The keeper of the gate to the Underworld that lay in the waters of Lerna was the Hydra. Excavations at the site were initiated under John L. Caskey in 1952, whose efforts initiated the series of publications of Bronze Age Lerna, "Lerna" I-V, inspiring many other publications. Lerna was occupied in Neolithic times, as early as the fifth millennium BCE, then was abandoned for a time before the sequence of occupation from the Early Bronze Age (Helladic period through the Mycenaean).