The room was dimly lit and only lit by a faint yellow lightbulb and the fireplace flames. A small group of men and women, clutching the sacred icons of the Greek Orthodox saints, danced and whirled across the floor to the sound of instruments: a Thracian lyre, a gaida, a tambourine. The dancers who surrendered to the music had their eyes closed.

Everyone sang together:

Constantine the little, little Constantine,
His mother had him, she took care of him when he was very young,
A message came for him to go to war
He saddles and horseshoes his horse in the night,
He lays silver petals, gold nails and a pearl on the saddle.

Their voices carried out into the rainy streets. A while later they started walking barefoot on burning coals in a kind of ecstasy.

Every year on May 21st, the Greek Orthodox Church celebrates Saints Constantine and Helen. In the small village of Lagadas, about half an hour outside of Thessaloniki in northern Greece, the festivities last three days and include a spectacular fire walking ritual called Anastenaria, whose word is derived from the Greek “Anastasi” and means resurrection.

In 2016 I traveled to Northern Greece to meet some of the people who keep these traditions.

Anastasios Gaintatzis’ family and close friends are some of the last remaining participants. The 85-year-old Gaintatzis is one of the oldest fire fighters in the country. His family, who once lived in what is now the Bulgarian city of Kosti in eastern Thrace, came to Lagadas in 1923 after the mandatory population exchange between Greece and Turkey.

The people who gathered here were members of a club founded by the Gaintatzis family in 1994 to uphold local fire-walking traditions.

Ethnographers believe the ritual has its roots in the ancient Greek festivals of Dionysus – and that pagan traditions have merged with Orthodox rites over the years.

Others believe in a local legend that traces the ceremony back to the fact that the Church of Constantine and Helena caught fire in Kosti hundreds of years ago. According to tradition, the voices of the saints in the Church were asked for help. The villagers entered the burning building to rescue the icons of the saints, and when they came out, neither the rescuers nor the icons were injured. They had been protected from the fire by the saints.

The Anastenaria ritual begins at the Konaki, a special shrine dedicated to the saints, where the icons are placed between the amanets (red handkerchiefs considered sacred by the fire wanderers) and other honors.

Then the musicians come and the party begins.

The firewalking ceremony is usually held outdoors, but in 2016, heavy rain forced the event indoors.

One of the group members placed large pieces of wood on the fireplace and when the hot coals formed everyone was ready to begin. The celebrants removed the carpet, spread the burning coal on the floor and walked on it one by one barefoot with closed eyes, almost drunk with the feelings of the moment.

Some participants walked slowly, others faster. They followed the rhythm of the music. I tried to pay close attention to their faces. They showed no signs of pain or discomfort. In fact, they seemed rather calm and peaceful.

When the first batch of coal had cooled, a second batch was taken from the fireplace and the ceremony continued unabated.

Even as a spectator, I felt a surge of emotion as I watched the fire walkers – and maybe even the deep mystery and divinity of the moment.

The Anastenaria rituals in Lagadas usually attract dozens of people from the area, but on the first day the bad weather kept most of the visitors away. In the next two days after the rain stopped, many people came to watch – and this time the fire barrel pit was built in an outdoor area near the Konaki, which was made available to the celebrants by the community.

Metal barriers were arranged in a large circle to protect the audience, and in the center members of the group lit a large fire on a pile of wood. When night fell, people gathered to watch. When the firefighters and musicians left the Konaki, it was pitch black outside. All the lights in the area went out and the only thing you could see was the burning coal. The crowd stared in silence as the firefighters stormed the embers.

After the celebration, the group gathered again at the Konaki and ate hot soup bowls to ward off the cold weather. They also offered me a bowl. Soon everyone except Anastasios Gaintatzis had left.

Mr. Gaintatzis has long tried to keep the custom alive by adding new family members and close friends to the group whenever possible. But it’s not an easy task, he said.

“It’s something that can’t be taught,” he told me. “It is the saints who call you.”