In a normal condition of things there should be here neither lake nor mud-pond, but only a plain with a river running through it, and disappearing in a hole at the foot of the mountain at the southern end. Mountains are so thickly strewn in Arcadia that streams cannot get around them, and so have to go through them. In this case the water was supposed to find its way out under the mountains to a point somewhat south of Argos, where it rushes out of the mountain side as a pure and full river, under the name of Erasinos. But such a hole, called a _katabothra_, was always likely to get clogged, and, as a stoppage might occur at a distance from the mouth, it might be very difficult to clear it out. In spite of great care this katabothra was, doubtless, sometimes stopped in ancient times. The horrible Stymphalian birds which Heracles killed typify, it is supposed, the pestilence which arose from such a stoppage. Such gigantic labors as forcing open the katabothra are quite in keeping with the character of Heracles's other labors, which included the purging of the stables of Augeas and the draining of the marsh of Lerna, typified by the killing of the Lernæan hydra. That birds should here be chosen to represent the evil seems an apt touch of local coloring; for several times in our stay around this lake the air was shaken by a rustling of wings, and flocks of birds that looked like wild ducks settled down into the water or flew up from it. As a proof that the water of the lake in antiquity was not up to its present level, we saw near the water's edge deep wheel ruts in the rock, which would now be deeply covered by the water in the spring (for besides the irregular variation, dependent on the more or less perfect working of the katabothra, there must always have been the regular variations, dependent on winter rains and summer drouth). Furthermore, standing on the imposing walls of the acropolis of Stymphalus, on a hill which projects from a mountain out into the marsh on its western side, one sees foundations of temples and other buildings of the lower town, hardly clear from water at the driest season of the year. Archæological excavations here would probably be particularly rewarding; but are absolutely impossible until the modern arrangements for draining the lake, begun some years ago, are carried to a higher stage of perfection than they have reached at present. Of course there is no better drinking-water in Greece than that which flows into Lake Stymphalus. It flows from the mountains round about. Kyllene contributes a large share. It is only when it lies in the basin and stagnates there that it becomes polluted. In Hadrian's reign an aqueduct carried from this source a copious supply of water to populous Corinth, furnishing both drinking-water about as good as that of Pirene and the great amount required in the numerous baths.