The sad remains of the Lernean spring.
The second labor was designed by Erystheus to make sure that Heracles wouldn’t survive. He therefore asked the hero to kill the Lernean hydra, a monster spawned by titans and brought up by Hera. This creature dwelled near in a spring or lake in Lerna near Argos and it was a terrible sight compared to the Nemean lion. This monster had nine heads and the middle one was immortal, its blood was poisonous and each time a head was cut off, two new ones sprang forth.
Heracles tried at first to kill it with his arrows but they were ineffective, then he tried to attack it with his club or a sickle (cutting the heads of) but this only made things so much worse. The hero was also attacked by a gigantic crab. However Heracles helper Iolaus came up with an idea and started burning the necks of each decapitated head, thus preventing it from growing out again. This way the hero and helper killed of all the mortal heads until only the immortal one was left, which Heracles buried under a huge rock.
As a last important act, Heracles had his arrows poisoned in the hydras blood, thus making them even more lethal.