[2] Thermos was not a city in the sense of a built-up urban centre like Athens, Argos or Corinth and until a late date the Aetolian League was a loose association with a tribal basis rather than a group of city-states.

The roof was tiled in terracotta, a recent innovation for the Greeks; the extra weight compared to thatch or wooden shingles was perhaps a factor driving the change to building with stone.

These include roof tiles, simas, at least two series of antefixes decorated in relief with human busts, a sphinx acroterion and 10 fragmentary metope plaques with painted representations.

It is argued that both sets are too large ("way too high"), at about 90 cm, for the function traditionally assigned to them in the wood-to-stone model, but instead demonstrate that "the Doric frieze was a decorative rather a structural feature" from the start.

[12] Recent excavations conducted by Professor I. Papapostolou for the Archaeological Society of Athens (Archaiologike Etairia Athenon) have confirmed that a) the building is likely to have been constructed after the end of the Mycenaean period c. 1000–900 BC; b) that the curious horseshoe shaped setting of stone slabs which appeared to surround the Megaron was only put in place after the Megaron had gone out of use and c) that the burnt stratum with the typical offerings of the later Geometric period (800–700 BC), attested at many Greek sanctuary sites such as Olympia and Delphi, intervenes between the slabs and the foundations of the Archaic temple which carried the painted metopes.

At the same time, three long stoas were built within the precinct and the spring just to the south of the temple (perhaps the original reason for the location of the site) was enclosed to form a fine stone-lined "fountain" or pool.

The Aetolians at this period embellished the sanctuary with astonishing numbers of bronze dedicatory statues but today only a few fragments (fingers and toes or horses' hooves) as well as the marble bases on which they stood, survive to illustrate this wealth.