Was Iznik’s “Underwater Basilica” the Site of the Council of Nicaea?

In 2014, three journalists flying in a helicopter over Lake Iznik in western Turkey happened to notice a faint outline in the murky depths. Upon further investigation, the shape was determined to be the remains of an early Christian basilica with two aisles and an apse flanked by anterooms on either side. In October 2023, the PBS program Secrets of the Dead popularized awareness of this so-called Sunken Basilica. Scholarly archaeological attention to these remains has focused on whether the building may have housed sessions of the Council of Nicaea. A related issue is whether this structure stands on the site of a prior temple of Apollo, as maintained by the Turkish overseer of the excavations, Dr. Mustafa Şahin. ETS member Dr. Mark Fairchild holds that the basilica dates to the turn of the fifth century, but was pre-dated by a wooden building (whose remains are no longer extant) which could have hosted conciliar sessions.

My paper will argue that the site probably was not home to an Apollo temple, but was a Christian martyrion centered on the grave of a martyr, perhaps the figure known a St. Neophytos (mentioned by Hieromonk Makarios of Simonos Petra, The Synaxarion). A late fourth century date is appropriate for the basilica, but I do not think it was preceded by a wooden building, unless perhaps it was a kind of pergola for refrigeria celebrations (akin to the Memoria Apostolorum in Rome). Certain comments by Eusebius (Vita Constantini 3.7.1) do not imply that the council met in a cramped, extra-mural basilica, but in the main meeting halls of the imperial palace complex at Nicaea. The nature of Constantinian councils demands this sort of venue. In addition, certain considerations of Tetrarchic politics prior to AD 325 do not allow for the construction of a Christian basilica at Nicaea between the Peace of the Church and the council.