Along the coast is the National Road Sector, where excavations have brought the city’s earliest occupation levels to light. Certain of these levels probably go back to the first half of the 7th century BCE, or before the establishment of Greek colonists at Argilos. Excavations in the section between the National Road and the beach were undertaken with the objective of identifying signs of what Perreault terms the pre- and para- colonization levels, the oldest of which are situated at an estimated depth of 6.5 m. The work thus far has taken place on an extremely large scale, given the levels of stratigraphic accumulation in this area requiring excavation, and the phenomenal quantity of pottery found so far, demanding processing and study.
Most recently, a 100 m2 surface area has been uncovered with a succession of levels containing burned areas and strewn with ceramics of diverse provenance: cooking vessels (probably local), ceramics from Thrace and the Chalkidiki, local and regional Greek wares, and also ceramics from distant production centres (East Greece, the Cyclades, Corinth, Athens, etc.). From a chronological point of view these levels are very homogeneous, with artifacts dating from the first half of the 6th century BCE. However, these trenches have been excavated only to a depth of 2.50-3.00 m. By 2002, many trenches had been excavated past the 2.0 m mark, revealing layers corresponding to the 1st and 2nd quarters of the 6th century BCE and the last years of the 7th century BCE. Finds from these layers enabled important work concerning the development of typologies for various early series of pottery, particularly regional and local products, as well as the revelation of information concerning early Greek settlements in the area. Much work remains to be done in this zone, and it will require precision excavation due to the highly complex stratigraphy.
Expansion of trenches in 2003 enabled a broader understanding of the occupation levels which are contemporary with the arrival of Greeks at Argilos. Excavation proceeded with greater caution, and the stratigraphy was clear enough to distinguish various chronological phases. Excavators isolated a thick layer of fill dating to the 2nd quarter of the 6th century BCE with high quality pottery from various centres of production, including Thrace (cooking pots), Olynthos (transport amphoras and skyphoi), and Andros (cups and lekanai), all of which are attested from the 7th century BCE. Various new forms of pottery appear in 6th century BCE levels. Of particular note are the impressive collection of Corinthian imports and significant number of kraters found in residential contexts. While local ware was also found, these types were from fill layers and their analysis (particularly in relation to comparative work) is made more difficult by the lack of published Thracian and Macedonian wares. At this stage of research it appeared that the Late Corinthian ware found at Argilos differed significantly from that found at nearby Thasos, suggesting significant differences between Greek communities situated relatively close to one another.
In 2004 and 2005 more trenches were opened, resulting in a total excavated area of more than 100 m2, from which all soil was sieved due to continual high concentrations of finds. The oldest levels of the entire side were found in the National Road district, dating back to the 1st half of the 7th century BCE, a period predating the arrival of Greek colonists. Overall, levels are very homogenous across the zone, with levels of the 1st half of the 6th century BCE found at depths of 2.5 to 3.0 m, whereas the earliest levels of occupation are found at depths of 6.5 m. Certain finds allowed extremely tight chronological control, such as in strata where Attic black figure, Corinthian, Ionic, and local sherds were found, all dating to 575-560 BCE. During this period the area was outside the settlement limits and was used for metal working and other industrial activities. An area of beaten earth was discovered with an associated apsidal kiln with central support. Although it is not clear if it had a domed top, it appears too small to be a domestic pottery kiln but could have instead been used for either the melting of metal or fabrication of metal tools. Two carbon installations excavated near the kiln provided the necessary charcoal fuel and date to the 2nd quarter of the 6th century BCE.
In 2006 two more structures were revealed which provide further evidence about the ancient settlement. An east-west wall was found running parallel to the coast with only a southern face since it is adjacent to the hill. A small north-south wall meets the first wall, bisecting it into two segments. Only a small part of the interior area was excavated and no objects were found other than a lump of clay. Contrastingly, the area outside the walls was very rich and was dated to the 3rd quarter of the 6th century BCE. Nearby, a floor level 20 cm above the level of the nearby industrial complexes was identified which had four post holes aligned east-west. These are likely the remains of a wall supported by wooden posts, part of a structure whose overall form is unclear. What is clear is that it is the only architecture on the site dating to before the middle of the 6th century BCE, and it cannot be dated past 550 BCE on the basis of several finds on the floor level.
Subsequent study seasons have involved the re-examination of 100 boxes of material, the photographing of diagnostic pieces, and the completion of geological sections and descriptive forms. Overall the zone is extremely rich in artifacts which cover chronological periods otherwise not known in the region, notably the 7th century BCE, a crucial period of the site which corresponds to the arrival of Greek colonists. There are many regional products found mainly on sites in the Chalcidice area and around the Thermaic gulf.