IZNIK, Turkey — On the second day of his first overseas trip, Pope Leo XIV visited the shoreline ruins at Lake Iznik where bishops gathered 1,700 years ago for the First Council of Nicaea, the 325 assembly that produced the creed still used in many churches today.
The first American pope stood beside Ecumenical Patriarch Bartholomew I amid the excavated remains of the basilica where early Christian leaders convened to settle divisive theological questions. Long submerged beneath the lake, the church’s apse and dozens of graves re-emerged in 2014 as waters receded, revealing the stones of a site important to Christian history.
At the lakeside, Pope Leo urged rejection of violence and religious extremism. “We must strongly reject the use of religion for justifying war, violence, or any form of fundamentalism or fanaticism,” he said, calling instead for fraternal encounter, dialogue and cooperation. The comment underscored a theme of his trip: pressing for unity among Christian denominations and encouraging collaboration among religions and communities. Speaking alongside Turkish President Recep Tayyip Erdogan, the pope warned that growing division and polarization imperil humanity’s future.
The Council of Nicaea was convened by Emperor Constantine to address a doctrinal crisis over the nature of Jesus. The most prominent opponent was Arius, an Alexandrian priest who argued that Jesus was the highest created being but not equal to God. The bishops rejected that view and affirmed that Jesus is “of one substance” with the Father, a phrase that became central to the Nicene Creed.
The basilica’s precise location came to light after aerial photographs of Lake Iznik were reviewed by Turkish archaeologist Mustafa Sahin, who said parts of the church had been under about eight feet of water. Locals had long noticed the stones when water levels fell—swimmers sometimes rested on them—but the more complete outline of the building only became visible as the shoreline shrank.
Christian unity persisted for centuries until the Great Schism of 1054 split Western (Catholic) and Eastern (Orthodox) Christianity over theological disagreements and competing claims of authority between Rome and Constantinople (now Istanbul). Ahead of his visit, Pope Leo issued an apostolic letter describing the Nicene Creed as a “common heritage of Christians,” written in a time when wounds from persecution were still raw.
At the exposed ruins, the pope and Patriarch Bartholomew shared a moment of silent prayer, a symbolic act of reconciliation on a site symbolic of early Christian agreement. The two leaders planned to follow that gesture with a joint declaration the next day, a further public sign of their efforts to bridge historic divides and foster a spirit of cooperation among Christian communities.