This was the first labour set by King Eurystheus, it was to kill the Nemean lion.
Hercules had been wandering around the area of Nemea when he came across the town of Cleonae. There he met who said that if Hercules killed the Nemean Lion within 30 days, the town would sacrifice a lion to Zeus. But if he did't return within 30 days or died the boy would be scarificed. Hearing this Hercules set of immediatly set of to find and kill the lion.
Whist Hercules was searching for the lions he fetched some arrows not knowing that the lions coat was impenarable and one of the strongest in the world. When he found the lion he shot at it, he then discoverd the coats protectivity due to the fact that all the arrows were bouncing off. He decided to take another approach. He blocked up one enterance of his cave and sent the lion in and then went in the other way. Once Hercules was in close quarters with the beast he stunned it with it's club and strangled it.
Once the lion had died Hercules tried to take the strong coat of but couldn't. Athena saw Hercules in disstres and told him to take the lions claw and cut the coat off. This is the strong Cape you sometimes see Hercules with.