Only the fortified acropolis, where the citizens of Kallion retreated in times of danger, is still visible. Built on the hill where the castle of Velouchovo stands today, it occupied an extremely privileged location at the end of the Vardoussia mountain range, where the valleys of Mornos (ancient Daphnos), Belesitsa, and Kokkinos meet. The fortified enclosure, which dates to the fourth and third century BC, is preserved to a height above the foundations at places. Together with the acropolis fortification walls it is over two kilometres long. Most of the population, however, resided on the lower slopes.

Several sections of the fortification walls, private homes, cemeteries, and public buildings, including temples, the bouleuterion, the theatre, and the agora, were uncovered during excavation. None of these monuments is now visible, as the entire area is submerged under the artificial Lake Mornos. Archaeological finds, such as vessels, coins, mosaics, jewellery, and inscriptions, are on display at the Archaeological Collection of Lidoriki.