In Greek mythology, Augeas (Αὐγέας) or Augeias (Αὐγείας), whose name means "bright", was King of Elis and husband of Epicaste. He is best known for his stables, which housed the single greatest number of cattle in the country and had never been cleaned until the great hero Herakles came along.
Augeas was the son of Helios and Naupiadame.
Herakles' fifth labour
The fifth task set to Herakles was to clean the Augean stables in a single day. The reasoning behind this being set was twofold: firstly, all the previous labors only exalted Herakles in eyes of the people so this one would surely degrade him; secondly, the amount of dirt ammassed in the uncleaned stable made the task surely impossible. However, Herakles succeeded by rerouting the rivers Alpheus and Peneus to wash the filth out.
Augeas was irate because he had promised Heracles one-tenth of his cattle if the job was finished in one day. He refused to honour the agreement. Herakles replied by sending an army against him, which was defeated in the passes of Elis by Eurytus and Cteatus, sons of Molione; but Herakles appeared on the scene, and slew the Molionidae, and with them their uncle Augeas and his sons. Herakles gave his kingdom to Augeas' son, Phyleus, who had been exiled for supporting Herakles against his father.
Heracles fifth labour, Zeus Temple Olympia
According to the Odes of the poet Pindar, Herakles then founded the Olympic Games:-
the games which by the ancient tomb of Pelops the mighty Herakles founded, after that he slew Kleatos, Poseidon's goodly son, and slew also Eurytos, that he might wrest from tyrannous Augeas against his will reward for service done. 
The Romans gave the constellation of Capricorn its name, taking it from part of a myth also concerning Pisces. To the Greeks, it was called the Augean Stable, since the sun (brightness - the meaning of the name Augeas) appears goes to rest (i.e. stable) there during the winter solstice.
Since this time was so dark, early greek religious ideas were that the darkness of the sky was due to the accumulation of sin throughout the year, thus the stable is extremely dirty and never cleaned before that year. These sins were said to be washed away as the sun arose again, and the next sign of the Zodiac is Aquarius, who is implicated in greek mythology as causing a great flood. The, factual, river Alphaeus drains the mountains, but runs mostly underground, thus was seen as having been diverted.
The milky way, in ancient times, in some myths, considered as dairy cows, and their milk, lies next to the constellation of Capricorn, thus giving rise to a reward of cattle for passing the task of Capricorn.
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