Heracles fighting Geryones.
The tenth labour is similar to the ninth in some ways as it contains the same type of side stories during a voyage to and from a distant land – it seems like there are even more minor deeds connected to this one than the earlier. The most important and famous episode is when Heracles raises two pillars, one on each side of Gibraltar. This is why the straits were known under the name of “the pillars of Heracles” during antiquity. Some ancient authors even believed that Heracles was responsible for creating the straits, others that he made the passage smaller to prevent sea monsters from reaching the Mediterranean (Diod. Sic. IV. 18. 4 ).
The labour itself began when Erystheus commanded Heracles to bring him Geryones oxen. These oxen grazed on an island so far away to the west that it was called Erytheia (the red) as is was to be found under the rays of the setting sun. Heracles manned a ship and travelled westwards, accomplishing many great deeds before he reach a terrible warm land which he blamed Helios, the sum (god), for. The hero tried to make the sun move a little further away, making it cooler, by shooting arrows at him. Trying to kill an immortal is however impossible and the effort fruitless. Most gods would also seek revenge after such a behavior but Helios found it amusing and wanted to help the brave mortal. He therefore gave Heracles a golden bowl or ship to continue his journey in and it is in this vessel that he reached Eryteia.
There he found the guardians of the flock waiting for him, first the two-headed dog Orthus (Cerberus sibling), which he killed with his club, and soon thereafter the giant Eurytion who also was killed. The third guardian, Menoetes, who was responsible for Hades cattle (that so happened to be tended together with the ones Geryones owned) noticed what was going on and he reported back to Geryones (Apollod. Epit. II.5.10).
Geryones was an unusually strange monster; he was composed of three men who were joined together at the hip. He faced Heracles in full armour but was shot dead by an arrow (The arrows were poisonous since the hero dipped them in the blood of the hydra) (Apollod. Epit. II.5.10).
Heracles then returned to Greece with the cattle, but Hera put gadfly among them and they ran away from him as he was passing the Hellespont. The hero had to gradually recapture them and managed to give them to Erystheus in the end. The cattle was then sacrificed to Hera by the king.