It is based on Herodotus’ description of the Athenian ‘Imerodromou’ or messenger who arrived in Sparta the day after he departed from Athens and also on well known historical events of that time. It has, therefore, been considered the nearest route to that which Pheidippides must have followed.
Briefly, Miltiades’ messenger started out of Athens on the ancient Iera Odos, or “sacred road,” up to Elefsis. From there he followed Skyronia Odos, a military road on the slopes of the Gerania mountains, and traveled through Isthmia, Examilia and Ancient Corinth. He went on to Ancient Nemea, thus avoiding the Epicratea of Argos, as it wasn’t in alliance with Athens, and he continued along the mountains between Argolida and Arcadia. He climbed the Parthenio mountain (1200 meters), where he encountered the God Pan. Descending the mountain, he continued in the direction of historical Tegea, one of the locations mentioned by Herodotus in his account about Pheidippides. He proceeded south toward Sparta. Upon his arrival in Sparta, he completed 1140 “stadia,” which equaled 246 kilometers.