In 2014 aerial photography revealed a submerged structure in Lake Iznik. The following year Mustafa Şahin, head of the Archaeology Department at Uludaǧ University in Bursa, began work at the site. It was immediately clear that the structure was a Christian Basilica and excavations suggested that the basilica was constructed in the fourth century. Of the fifteen known Byzantine Basilicas in ancient Nicaea, this one is the earliest. Work at the site also exposed thirty-six cappuccino tombs, both in and around the basilica. In 2017, I was asked to collaborate with Şahin on research at the site. The archaeological work at the site has raised a number of questions. How was the basilica submerged? Turkiye is located on the Anatolian Sub-Plate which is considered the world’s most active seismic plate. Did seismic activity submerge the structure and if so, when? Was this structure originally a temple dedicated to Apollo, which was later converted into a Christian Basilica? Was this structure a martyrion, dedicated to a saint who was martyred at the site sometime during the years prior to the Edict of Milan? Was this structure the church used for the First Council of Nicaea in AD 325? This paper examines ancient literary sources, the archaeological evidence and utilizes technological resources to answer some of these questions. My book, The Underwater Basilica of Nicaea: Archaeology in the Birthplace of Christian Theology, detailing the history and research at ancient Nicaea is currently in production and will be available this summer 2024 with IVP Academic.