The present-day settlement of Sougia is built on the site of ancient Syia, which flourished mainly in the late Roman times. Underneath the surviving cemeterial temple of Saint Panteleimon there are the remains of a three-aisled basilica with a 20.80m x 12.40m narthex, which has been excavated by A. Orlandos.
The aisles are separated by low pillars, over which stood an archway with white marble pillars, two of which had inscriptions with devotions to Saints Panteleimon and Demetrius. One more pillar separates the central aisle from the sanctuary, in the center of which is preserved the lower plate of the alter and the bases of the columns of the ciborium. Three consecutive spaces, possibly baptisteries, were attached to the northwest of the temple.
The mosaic floors that are preserved in perfect condition, in the middle aisle and the narthex, include geometric shapes of intersecting circles and semicircles, flakes, braids, as well as representations of peacocks and a deer, as well as amphorae with ivy shoots. The floor construction has been attributed to a 6th century workshop, that was also active in the area of Argos.
To the east of the basilica and to the east of the archaeological site are the remains of three more basilicas that demonstrate the indicate the power of Sougia in the early Christian times.