The reform was radical. Cleisthenes mixed Athenians from different parts of Attica into each new tribe, scrambling kinship and geography in a single stroke. To give each tribe an identity, he asked the Delphic oracle to choose ten legendary heroes from a list of a hundred candidates. The chosen ten became the eponymous heroes, the namesake founders. Erechtheus. Aigeus, the father of Theseus. Leos. Akamas. Hippothoon. The names are mostly forgotten now, even by people who know Athens, but for two centuries every Athenian citizen carried one of them in his official identity. You were not just an Athenian; you were of the tribe of Erechtheus or the tribe of Leos, and your tribe drew lots, fielded its share of the army, sent its share to the Boule, and read its announcements at this monument.

The ten bronze statues stood on a long marble pedestal surrounded by a wooden fence on stone posts, with bronze tripods at each end. Above the heroes' heads, officials pinned the tablets that mattered: lists of citizens called for military duty, indictments to be tried, decrees of the assembly, the calendar of festivals. As Athens passed through the upheavals of the Hellenistic age, however, the monument itself became a barometer of who was winning. In the late 4th century BC, two new tribes were created and two new statues added, honoring the Macedonian kings Antigonus I and Demetrius Poliorcetes, who had liberated Athens from one set of overlords. Eighty years later, Ptolemy III of Egypt was added when Athens leaned Egyptian. Then, when Philip V of Macedon besieged the city in the Second Macedonian War, the Athenians hastily removed the statues of Antigonus and Demetrius and added a sculpture of Attalos I of Pergamon, who had sent ships to help. Finally, in the second century AD, a statue of the emperor Hadrian was placed at the end of the row. Each addition required modifying the pedestal, sometimes the fence, sometimes both. The monument's archaeology, on close inspection, reads like a chronicle of Athenian foreign policy.

When the American School of Classical Studies began excavating the Agora in 1931, this long fenced peribolos was one of the first major structures to come up. The early reports labeled it 'Periphragma,' a generic term meaning fenced area, and admitted that no one was sure what it was. The size and the placement next to the Bouleuterion, the council house where the Boule of Five Hundred met, suggested importance. But the geographer Pausanias, writing in the second century AD, had said the Eponymous Heroes stood 'above the Tholos,' and the Tholos was elsewhere on the map. It was not until 1949 that Eugene Vanderpool published the argument that finally settled it. Pausanias's word, he proposed, should be read as 'further away from' rather than 'above,' and the Tholos confusion came from a misreading of a smaller building called the Prytanikon. The peribolos was the Eponymous Heroes.

Walk through the Athens Agora today and you find the long sill, slightly slumped at the north end where the ground falls away, with a partial reconstruction of the wooden fence on the western side. The bronzes are gone, melted down for their metal in some late antique furnace. The wooden tablets that once made this stone the most-read piece of public information in the ancient world rotted away within a generation of the city's last decree. The pedestal itself is poorly cut by the standards of Periclean Athens; gaps between the stones, no clamps, a foundation in shallow earth. It was built quickly, repaired carelessly, modified often. It was a working object, not a monument to itself. Which makes it, in its way, the most democratic structure in the Agora.