Even by more modest modern estimates, though, the victory at Marathon was one of great symbolic importance: the idea of individual cities coming together to fight the invading 'Barbarians' (at that time, the word only meant the people who spoke a language unintelligible to the Greeks) was quite novel, and would later form part of patriotic speeches, political propaganda, and even legendary material.
The battle, along with that of Salamis a decade later, was significant enough to start the Greek tradition of erecting trophies to commemorate any martial victory and make the enemy think twice before returning. The etymology of 'trophy' is quite telling: the Greek word is tropaion, which derives from tropi, the point where enemy lines break and turn to retreat.
The original trophy must have been rather makeshift, perhaps a tree close to the turning point, decorated with armour parts and weapons belonging to the defeated, and dedicated to the god who took credit for the victory. Thirty years after the battle, however, the Athenian democracy was approaching its greatest splendour, what would be later referred to as the Golden Age; other monuments were being erected to commemorate Marathon, such as the Athena Promachos in the Acropolis, and the Marathon monument at Delphi.
In that context, a ten-metre Ionic column of Pentelic marble replaced the previous trophy. The size of the capital has led archaeologists to believe that another marble element, perhaps a statue, was also placed on top of the column. Visitors today are only able to see a replica of the column in situ, close to the Christian chapel of Panagia Mesosporitissa, while fragments of the original column are on display at the Marathon Museum.