BIBLE HISTORY DAILY

Where Was the First Council of Nicea?

Investigating new finds from Nicea’s underwater basilica

An early promulgation of the new faith, the Nicene Creed is a foundational document for all major Christian denominations. In one of the most consequential statements, it recognized Jesus as fully divine and of the same substance with God the Father. It was adopted in 325 CE by the First Council of Nicea. But where in Nicea?

Writing for the Fall 2025 issue of Biblical Archaeology Review, Mark R. Fairchild brings forth two important clues that may finally help solve this mystery. A retired professor of biblical studies at Huntington University and a specialist in the Hellenistic and Roman periods in Asia Minor, Fairchild examines an eyewitness testimony about the First Council of Nicea vis-à-vis new archaeological evidence from the only fourth-century church discovered in Nicea (modern İznik in northwestern Turkey).

In his article, “Where Was the First Council of Nicea?” Fairchild first presents what the bishop of Caesarea and church historian Eusebius has to say about the location of the church assembly, at which he personally took part. Writing about the initial sessions of the council, Eusebius states that they took place in “a house of prayer,” i.e., a church. According to his eyewitness account, the venue was first a bit too small until, “as if extended by God,” it was able to accommodate all the church dignitaries. The concluding sessions were then moved to Emperor Constantine’s palace inside the city. The only known fourth-century church in the city is the so-called underwater basilica, the recent discovery of which was covered in Biblical Archaeology Review and a PBS documentary featuring 3D recreations of the monument. Can this be the location of the initial sessions of the First Council of Nicea?

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To be precise, the basilica is not located within the walls of the ancient city. Although it originally stood on the shore of Lake İznik (Lake Ascania, in antiquity), it was later swallowed by the rising waters of the lake and was noticed through aerial photography only in 2014. As its modern moniker reveals, the ruins of the church are still mostly submerged, which poses challenges to archaeological exploration. But why was this church built outside the city walls in the first place?

After several seasons of excavation, which begun already in 2015, archaeologists now believe that the large structure visible today begun as a small martyrion—a shrine honoring a Christian martyr. We know from written sources that in 303, only a decade before Emperor Constantine’s decriminalization of Christianity, St. Neophytos was martyred on the shores of Lake Ascania (see first image above). An improvised shrine was likely erected at the spot shortly after his death and may correspond to the small rectangular structure preserved under the apse of the later, large basilica.

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When Christianity was legalized, in 313, this initial sanctuary was expanded and must have been the church that Eusebius mentions as the venue of the First Council of Nicea in 325. While the initial shrine was built with stone, however, this new basilica was built largely with wood, which can be postulated from the wooden beams and large numbers of nails recovered from within and around the structure. Eventually, this basilica was rebuilt in stone, before it collapsed in an earthquake sometime in the 11th century and was swallowed by the lake.

To explore all the evidence and discover why there are so many graves in and around the basilica, read Mark R. Fairchild’s article “Where Was the First Council of Nicea?” published in the Fall 2025 issue of Biblical Archaeology Review.

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Related reading in Bible History Daily

The Nicea Church: Where Did the Council of Nicea Meet?

Who Was St. Nicholas?

All-Access members, read more in the BAS Library

Nicea’s Underwater Basilica

Century Mark: First Council of Nicea