Overview
There are two tumuli at Marathon, Greece. One is a burial mound (Greek τύμβος, tymbos, tomb), or "Soros" that houses the ashes of 192 Athenians who fell during the Battle of Marathon in 490 BC. The other houses the inhumed bodies of the Plataeans who fell during that same battle. The burial mound dominates the plain of Marathon, where the eponymous battle took place, along with the tumulus of the Plataeans, and a victory column erected by the Athenians to commemorate their victory over Darius' Persian expedition. The tumulus is encompassed in a park today.
Battle of Marathon
The Battle of Marathon took place on September 12, or possibly August 12, 490 BCE at the plain of Marathon. Athens and its ally Plataea, some 11,000 hoplites in total, attacked a Persian expeditionary force of some 25,000 infantry and 1,000 cavalry, with 100,000 armed sailors acting as reserves. The Athenian forces attacked down a hillside onto the coastal plain, and using the momentum of their tightly packed, heavily armored formation routed the less disciplined Persian flanks, which were unused to fighting heavily armored troops. The subsequent rout left the Persian center exposed and as a result the Persians suffered high casualties as their command structure fell into disarray and as soldiers scrambled onto their ships. Herodotus claims that the Greeks counted 6,400 dead Persians on the field, but could make no account for those who fled into the swamps off to the north of the battlefield. Herodotus states that the Athenians lost 192 men in the battle and the Plataeans lost 11.
Monuments
From Wikipedia (CC BY-SA 4.0).