A key insight into the importance of early Christian history has been hidden beneath a lake in northwestern Turkey for over 700 years, until its ruins were exposed as the lake continued to retreat due to climate change. The 4th-century basilica of Nicaea, found in Iznik, a small town several hours from Istanbul, is said to mark the site of one of the Church’s most important gatherings.

The basilica, also known as the Basilica of the Holy Fathers, marks the site where the First Council of Nicaea met, 12 years after the Roman Empire legalised Christianity, ending years of persecution, torture and death. In AD 325, approximately 1,700 years ago, Constantine the Great convened 318 bishops who, after two months of intense debate, drafted the Nicene Creed, a Greek-language declaration of faith that remains central to Christianity to this day. 

On Friday, Pope Leo XIV visited the site to mark the 1,700th anniversary of the council.

According to archaeologist Mustafa Sahin, who first identified it from aerial photos in 2014 and has led the excavation, the first six years of which were underwater, the basilica was built in AD 380.

“When it was first discovered, the ruins were 50 metres (164 feet) offshore and two metres underwater,” explained Mr Sahin, a professor who heads the archaeology department at Uludag University in the nearby city of Bursa.

“However, due to global warming, the lake’s water started receding in 2020 and now the entire church is above the water.”

Mr Sahin added that the basillica stands on the site of an even earlier church, built where a a 16-year-old called Neophytus was killed for his faith in AD 303, during an era of fierce Roman persecution. The teenager had been whipped and stoned, before being beheaded “for refusing to offer sacrifices to pagan gods and worship idols”.

The First Council was held in a wooden church at the site, but this building was destroyed in a 9-magnitude earthquake in AD 358. The stone basilica was built on the same site around two decades later. This stood for seven centuries until it was also destroyed in an earthquake in 1065, with the ruins subsequently disappearing beneath the rising waters of the lake 200 years later.

The team’s research has also led to the discovery of around 300 graves, including 11 belonging to children, many of which suggest the deaths were violent, leading to Mr Sahin describing the church as “a martyrs’ graveyard“.

“We have excavated only 27 of these graves and have observed signs of torture – broken arms and legs, skulls with holes in them, perforated craniums, showing us that those buried here were tortured and killed,” he said. “This was not just a regular church cemetery but rather a place of martyrdom, a very significant church for Christians.”