A relief depicting the labours of Heracles - they sixth labour at the left.
The modern view over the Stymphalus acropolis cliff and what's left of the lake. The setting must have been absolutely stunning during antiquity.
The Stymphalian birds were the pets of Ares, had brazen claws and beaks and arrows instead of feathers. A great number of these creatures haunted the inhabitants of the central Peloponnesus and lived of their flesh. Erystheus commanded Heracles to expel these birds and he went to the lake where they dwelled (conveniently called Stymphalus). Athena helped the hero by giving him a brazen rattle and he used this to scare the birds who took flight – they were vulnerable in the air and he shot some down, others took refuge at the island of Aretisa (where the Argonauts found them later).