Late Neolithic (ca. 3500‒3000 BC)
The occupation of the site at the end of the Neolithic Period is attested by a few pottery sherds and stone artefacts-obsidian and silex- found on the summit of the acropolis as well as on the plain, near the shore. Were these already permanent habitations or merely temporary refuges? It is difficult to give a clear answer, because no structures have so far been found. Whatever the case, the area was probably suitable for settlement: the acropolis, a landmark in the landscape and a privileged observation post overlooking the surrounding plain, offers a secure shelter in proximity to a natural port. The vestiges of a Neolithic settlement may still lie beneath the modern town, protected by groundwater and thick layers of clay.
Early Helladic Period (ca. 3000-2000 BC)
The following period, the Early Helladic Period, is better known. The site was more densely occupied, especially on the plain. A major settlement replaced the Neolithic one on the coast; it lasted nearly a millennium, until the dawn of the Middle Helladic Period in ca. 2000 BC. Several buildings have been discovered, one of which has been interpreted as a granary, and some 800 stone-working tools, along with stone chips, may indicate the existence of a stone-cutting workshop. The smooth, thick-walled beige pottery that has been discovered anticipates the Minyan ware characteristic of the Middle Helladic Period. An exceptionally well-preserved potter's kiln, now on exhibit at the Eretria Museum, may belong to this phase: a few sherds from the Early Helladic Period were discovered in vents from the kiln's furnace, but without radiocarbon dating we cannot ascertain its precise date. The settlement must have been extensive, to judge by recent discoveries made about 150m away in the sanctuary of Apollo Daphnephoros, where a deep trench reached occupation levels from this period. Artefacts on the site dramatically decreased ca. 2000 BC: apparently the settlement was deserted. This is corroborated by the analysis of sediments preserved in the soil: the coastal area turned into a lagoon, and about a thousand years went by before it became suitable for human habitation once again.
Middle Helladic Period (ca. 2000-1600 BC)
Because the coastal settlement disappeared, flooded by the waters of the lagoon, settlers moved to the top of the acropolis, in order to find a more secure shelter from the encroaching sea. The summit was leveled off and a large retaining wall was built on the south side of the resulting terrace. A village-like settlement prospered there, with houses and small streets; natural cavities in the stone were used as tombs. The pottery consists essentially of domestic wares and a few more refined vases in smooth gray clay -the Minyan pottery that is found all over Greece at this period. The presence of spindle-whorls and loomweights points indirectly to pastoral activities.
Late Helladic Period (ca. 1600-1100 BC)
The acropolis was inhabited until Mycenean times. Nonetheless, habitation became more sporadic: only a few pottery sherds and what has been interpreted as an observation post, erected on older foundations, have been excavated. That is very little in comparison with the remains of earlier and later periods. However, in the Homeric tradition, Eretria goes back to the heroic age: in the famous Catalog of Ships in the Iliad (II, 537), Eretria is one of the seven Euboean cities that provided Agamemnon with boats and troops for the expedition against Troy. But there is a great gap between this narrative, which was composed a few centuries later, and the archaeological remains. The Mycenean past of Eretria remains to be discovered, unless it should be sought at the neighboring sites of Lefkandi or Paleoekklissies.