By September of 490 B.C., the advancing force of Persia -- then the most powerful empire in the world -- reached Marathon, anchored its fleet in the bay, and made plans to attack Athens. The Athenians sent their swiftest runner, Pheidippides, to Sparta to ask for help, and marched their entire army of about 9,000 men north to Marathon. When Pheidippides reached Sparta (some say that it took him about a day and a half -- clearly the gods were on his side), the Spartans said they would be delighted to join the Athenians, after the conclusion of an important Spartan religious festival observing the full moon. This was widely thought to be a delaying tactic, and Athens prepared to stand alone -- and did, except for a small contingent of about 1,000 soldiers from the town of Plataea in Boeotia. The Persian force was at least 24,000 strong.

For some days, the two forces eyed each other, but neither attacked. Then, before dawn on September 12, the Athenians launched a surprise attack. As the Athenian right and left wings forged forward, the center gave way -- but when the Persians pressed forward, the Athenian flanks surrounded them and the serious slaughter began. Many of the Persians tried to flee to the safety of their ships, anchored offshore, but were cut down in the marshy plain that lay between the battlefield and the sea. By nightfall, the victory was won, and Pheidippides was again dispatched, this time to run to Athens with news of the victory at Marathon. Pheidippides burst into the Athenian Agora, shouted, "We have won," and fell dead from exhaustion. Today's marathons commemorate Pheidippides's run. (If you want information on the annual rerunning of the Marathon in Nov, check out www.athensmarathon.com.)

Although the Athenians won the battle at Marathon, the Persian navy set sail for Athens. The weary Athenian army marched back to Athens and prepared to do battle again, but the Persians, after sailing up and down the coast of Attica, reversed course and returned to Asia Minor. Ten years later, they would be back -- only to be defeated decisively in the Battle of Salamis.

The Athenian victory at Marathon, against such great odds, became the stuff of legend. Some said the Athenian hero Theseus himself fought alongside his descendants. Others said that the god Pan bewitched and confused the Persians, leading them to plunge to their deaths in the swamp -- leading them, in short, to panic, the word derived from the god's name. According to one legend, Pan appeared to Pheidippides as he ran with news of the victory to Athens. Pointedly, Pan asked why the Athenians built so few shrines to him -- a situation quickly rectified throughout Attica.

Although it was customary to bury war casualties in the Kerameikos cemetery in Athens, the 192 Athenian dead from this astonishing victory were cremated and buried together in the mound that still stands. When the Athenian mound was excavated in the late 19th century, quantities of ashes and burned bones were found.

Half a millennium after the battle, when the traveler Pausanias visited Marathon, he wrote, "Here every night you can hear the noise of whinnying horses and of men fighting." Indeed, there are those today who claim to have heard sounds of battle on moonlit nights at Marathon.

The excellent Marathon museum is several miles from the battlefield but is signposted both there and on the main road. The collection includes finds from the battlefield and other sites, including startling imitation Egyptian statues from a local shrine, possibly built by Herodes Atticus, the great 2nd-century-A.D. benefactor born near Marathon. Herodes Atticus, who owned a number of luxurious villas in Greece, seemed to be almost incapable of taking a day trip without building a fountain, shrine, or temple to commemorate his visit.

If you're not bothered by swimming near the marshy swamp where so many Persians drowned, you can take a dip and enjoy a bite at a taverna along the coast. Most tavernas close off season, although some open on the weekend. Nearby is the pristine beach of Schinias. Closer to Marathon is a very good, but busy, private beach called The Boat (www.karavi.gr). You can also visit the Marathon Run Museum, Junction of Marathonos Avenue and 25 March Street, Marathon Town (tel. 2294/67-617; www.marathon.gr), opened in 2004, which chronicles the history of the Olympic marathon race, from Athens 1896 to the present day. Most of the photographs, posters, and drawings were provided to the museum by the International Olympic Committee from the Olympic Museum Lausanne. The Marathon Run Museum is open Tuesday through Sunday 9am to 9pm.