The archaeological site of Ancient Sikyon extends across a plateau on the hill of Vasilikou. It consists of the excavated section of the Agora of the Hellenistic and Roman city, the Theatre, the Stadium, and the Roman Baths (Balaneion), which have been converted into a museum.

In the Agora, a temple has been excavated, dating from the Archaic to the Hellenistic period based on its construction phases. During the Early Christian period, it was converted into a Basilica.

In the southwestern part of the Agora, at the foothills of the Hellenistic acropolis, the Gymnasium-Palaestra stands out, dating back to the Hellenistic and Roman periods. The monumental complex spans two terraces (levels), connected by three staircases. Two fountain structures are notable, located along the retaining wall of the upper level of the building.

In the eastern excavated part of the Agora, the Bouleuterion and a long portico have been uncovered, constructed in the 4th century BC. During the Roman period, the Bouleuterion was converted into Baths (public baths), while the portico underwent repairs for use as workshops.

The Theatre, carved into a natural hollow on the slopes of the Hellenistic acropolis, dates back to the late 4th century BC. It consists of the cavea, orchestra, and stage, while two vaulted passageways at the ends of the cavea for the entry of spectators are unique examples of Hellenistic architecture. During the Roman period, additions were made, mainly to the stage building.

The Stadium, located to the west of the Theatre, although not excavated, is outlined by the morphology of the land. At the southern end, the spina is distinguishable, while the elongated track ends in retaining walls that supported the fill at the northern end.