The marathon is a long-distance running event with an official distance of 42.195 kilometres usually run as a road race. The event was instituted in commemoration of the fabled run of the Greek soldier Philippides, a messenger from the Battle of Marathon to Athens, who reported the victory. The marathon was one of the original modern Olympic events in 1896, though the distance did not become standardized until 1921.
More than 500 marathons are held throughout the world each year, with the vast majority of competitors being recreational athletes as larger marathons can have tens of thousands of participants.
There is debate about the historical accuracy of this legend. The Greek historian Herodotus, the main source for the Greco-Persian Wars, mentions Philippides as the messenger who ran from Athens to Sparta asking for help, and then ran back, a distance of over 240 kilometres (150 mi) each way. In some Herodotus manuscripts, the name of the runner between Athens and Sparta is given as Philippides. Herodotus makes no mention of a messenger sent from Marathon to Athens, and relates that the main part of the Athenian army, having fought and won the grueling battle, and fearing a naval raid by the Persian fleet against an undefended Athens, marched quickly back from the battle to Athens, arriving the same day.
In 1879, Robert Browning wrote the poem Pheidippides. Browning’s poem, his composite story, became part of late 19th century popular culture and was accepted as a historic legend.There are two roads out of the battlefield of Marathon towards Athens, one more mountainous towards the north whose distance is about 34.5 km (21.4 mi), and another flatter but longer towards the south with a distance of 40.8 km (25.4 mi). It has been argued that the ancient runner took the more difficult northern road because at the time of the battle there were still Persian soldiers in the south of the plain.
Mount Penteli stands between Marathon and Athens, which means that, if Philippides actually made his famous run after the battle, he had to run around the mountain, either to the north or to the south. The latter and more obvious route matches almost exactly the modern Marathon-Athens highway, which follows the lie of the land southwards from Marathon Bay and along the coast, then takes a gentle but protracted climb westwards towards the eastern approach to Athens, between the foothills of Mounts Hymettus and Penteli, and then gently downhill to Athens proper.