The
Lernaean Hydra or
Hydra of Lerna (,
Lernaîa Hýdra), more often known simply as the
Hydra, was a
serpentine water monster in
Greek and
Roman mythology. Its lair was the lake of
Lerna in the
Argolid, which was also the site of the myth of the
Danaids. Lerna was reputed to be an entrance to the
Underworld and archaeology has established it as a sacred site older than
Mycenaean Argos. In the canonical Hydra myth, the monster is killed by
Heracles, using sword and fire, as the second of his
Twelve Labors.