The traditional origin of the marathon comes from the story how a herald named Phidippides ran the 26 miles from Marathon to Athens to announce the Greek victory and died on the spot.
In the 5th century B.C., the Persians invaded Greece, landing at Marathon, a small town about 26 miles from the city of Athens. Phidippides was sent by the Athenians to Sparta to ask for help; a man named Eukles announced the victory to the Athenians and then died.
Later sources confused the story of Phidippides with that of Eukles. Although most ancient authors do not support this legend, the story has persisted and is the basis for the modern-day marathon.
The modern Olympic marathon is approximately 26 miles and usually takes over 2 hours for athletes to finish.