Kallipolis, or Kallion, the easternmost city of Aetolia, centre of the Kallian community and probably of the entire Aetolian nation of the Ophioneids, is located northwest of Lidoriki, at the site of the Velouchovo Castle. Kallion has been inhabited since the Geometric period, but it was not until the fourth century BC that it was founded as a proper urban centre, like the rest of the Aetolian cities, which gradually formed the Aetolian League, or confederation. A fortification wall was built to protect the new city and all the religious, financial, and political activities of the surrounding rural communities were sheltered inside it. Thucydides (3.96.3) mentions the citizens of Kallion as the westernmost community of the Ophioneids. Pausanias, on the other hand, and Stephanos Byzantios, who calls the city Sollion and Phakion, refer to Kallion as the Ophioneid capital. Hellenistic inscriptions use the name Kallipolis for the city.

Kallion occupies a strategic location near the crossing of the valley of Ano Dafnos and the Steno pass, the only route from Thessaly and the valley of the Spercheios river towards the hinterland of Aetolia and Naupaktos. This was the route taken by the Gauls during their attack of Aetolia in 279 BC, which led to the fall and destruction of Kallion, the atrocities committed against its inhabitants, and the terrible revenge of the Aetolians (Pausanias 10.22.3-7). The citizens of Kallion rebuilt their city after the Gaulish raid and became again actively involved in the history of the area. Kallion, however, is not mentioned in any written sources after the middle of the second century BC and does not reappear until the ninth century AD, when Lidoriki is reported as the See of the bishop. Lidoriki replaced Kallion as the administrative centre of the mountainous area of Doris. Fourteenth and fifteenth century sources mention only the castle of Lidoriki, which can be identified with the remains of Medieval buildings and fortifications at the site of the ancient acropolis.

After excavations by Professor Petros Themelis in 1977-1979, the city's public buildings and cemeteries were submerged under the artificial lake of Mornos.