A city in Arkadia (Arcadia).
During the Trojan War, Agapenor mustered Achaian (Achaean) soldiers from sites throughout Arkadia including—Stymphalos, Enispe, Mantinea (Mantineia), Orchomenos (Orchomenus), Parrhasia, Pheneos, Rhipe, Stratie, Tegea, and the slopes of Mount Kyllene (Cyllene).
A generation before the Trojan War, Herakles (Heracles), son of Zeus, was required to perform twelve labors. The sixth labor was to rid Stymphalos of an infestation of birds.
It's easy to believe that the classical Greeks, Romans and later writers (up to the present) weren't satisfied with the fragmentary condition of the ancient texts and sacrificed symbolism and subtlety for the sake of drama (like imagining the birds to be man-eaters) and thus inflicted their personal literary preferences on posterity.
Herakles entered the woods around the lake near Stymphalos with his bow and a pair of krotalas—castanet-like clappers that were made by the god Hephaistos (Hephaestus) and given to Herakles by the goddess Athene (Athena). The idea was to frighten the birds with the krotalas and then shoot them with his bow when they took flight. This labor doesn't seem too dangerous or laborious but we can only assume the task was beyond the abilities of other men simply because Herakles was sent to do it.
| References: Homer, Iliad book 2, line 608 |