Abstract
The remains of the basilical church lie approximately in 2 or 3 meters of depth, and 50 m from the shore of the lake, outside the city walls that surround the ancient city of Nicaea. The underwater archaeological excavations at the basilica remain are being launched under the auspices of the Iznik Archaeology Museum with the permission of the Ministry of Culture and Tourism in 2015.
In 2019, excavation was carried out in the atrium where we thought a water well was situated. This is because the British pilgrim, Willibald, pointed out that the site of the 1st Council had a rectangular open-roofed courtyard with a sacred source of oil in the middle. Although we went down 60 cm deeper than the foundation walls, we could not find the bottom of the well. However, a large number of ceramics, glass bracelets, or Scyphate coins (cup-shaped coins) were found indicating the 13th century. It was also found that the well was filled with stone. Therefore, we think that the structure was definitely abandoned in the approximately 12th century and then sank into the lake waters.