In 1983, south of Basilica High Priest Peter's atrium,  was discovered the baptistery that by the drawing and his dimensions is considered unique in the Hellenic space.

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The “Fotistirio” (illumination) in the east is square and it surrounds elevated circular pillar in which they stepped eight columns. In the center octagonal baptistery.

Impressive marble inlay on the floor. Epigraph on the west doorsill of the circular pillar, mentions that the constructor or donator of this layer was Polyhronios «for wish». Western of “Fotistirio” (illimination) there is a three aisled “outer” house.

It is probable that the baptistery is considered contemporary to the first Basilica of High Priest Peter.