One of the great population movements of modern times was the "exchange of populations" that took place in 1923 between Turkey and Greece. Neil Trevithick recently visited northeastern Turkey with the descendants of the Pontic Greeks, who were forced to leave more than 90 years ago.
It is a hot, sunny, crystal-clear, high-altitude day and we are climbing the endless steps up to the Soumela Monastery perched high up a cliff face.
We are in the foothills of the Pontic Alps near Trabzon in the far north-east of Turkey.
Nearer to Georgia, Baku and the mountains of the Caucasus than to Istanbul, here the ancient Greeks fished the waters of the Black Sea and cropped the hazelnut forests of the coastal plain below us.
Pontic Greeks from all over the world come to remember their roots here
Jason and his Argonauts passed along this coast, having left the terrible clashing rocks of the Bosphorus behind, en route for Georgia where they knew that the locals panned for gold using goats' fleeces.
Much later, this monastery became the centre of an Orthodox Christian community that thrived for more than 1,000 years in the Pontus, now called the Black Sea Region of Turkey.
And on the Feast of the Virgin, Pontic Greeks from all over the world come to remember their roots here.
'Best day in my life'
Breathless at the top, surrounded by Russian, Turkish, Greek and English voices, we find Zoyana Delios from Richmond in Virginia.
She is here on her first visit. Her grandparents held Russian passports and left Trabzon for Novorrossiysk in Russia on the other side of the Black Sea in 1922.
When communism turned on the Orthodox Church, they went to Greece and eventually to the United States.
Sotiria Liliopoulos has come here from Sydney. Her father used to live in Matsouka nearby and worshipped here as a child.
In her late 60s, she is small but determined and has a solid Greek accent despite living much of her life in Australia.
Sotiria has come, in her words, "to honour him".
Her father and mother (both 98 years old) are living in Sydney.
"He's always wanted to come back to Trabzon but first politics and now his health have held him back."
Satiria Leiliopoulos tells us she phoned home last night and her family were gathered around the telephone, celebrating the fact that one of them was at Soumela, raising glasses of ouzo to her.
"This is the best day in my life," she says, "visiting my roots."
Like many visitors, she is taking a pot of soil back with her so that she can give some of the earth of the Pontus to her parents.
These long-distance journeys are necessary because, in 1923, modern Greece and Turkey agreed to a huge exchange of populations.
Christians were to leave Turkey and go west to Greece, some one and a half million of them.
And around a million Muslims were sent east from Greece to Anatolia in Turkey.
Local musicians play the kemenje, similar to the ancient lyre
The idea that people of different religions could not live together, as they had done for centuries, and had to be moved wholesale into an utterly different geography and culture has caused untold misery to generations of families.
But many Turks are now happy to see these Pontic Greeks come and visit.
Late at night at a wedding celebration in a local park, one young Turk says to me, "Greek culture and Turkish culture the same."
They're like estranged brothers these people, moving slowly towards understanding.
That exchange of populations in 1923 was not one of nationality but of religion.
If you were Pontic and Muslim you could stay here, and a few did, so we went to look for them up in the mountains.
Head is spinning
After a tortuous six-hour journey along dirt tracks, we arrive in the high meadows behind Trabzon for a festival of kemenje music.
Hundreds of people in a huge circle dance in the mist - two steps to the left, two to the right - holding hands raised to chest height.
The people here are Muslim, of course. The usual posters of Ataturk hang from the pylons but the village language is Pontic and Pontic is really Byzantine Greek.
The real shock is in hearing the language because what I hear is ancient Greek
Their ancestors probably converted to Islam in the 17th or 18th Century for any numr of pragmatic reasons.
I am standing in the cold, eating a barbecued corncob cooked on one of the braziers glowing at the edge of the dancing area, and the real shock is in hearing the language because what I hear is ancient Greek.
When they say "I don't want", they use the ancient "ouk" sound and say "oothello".
This is where Xenophon fled after his defeat at the hands of the Persians. Jason's Argonauts would have been able to converse with these people.
The local kemenje is the same instrument as the Greek lyre.
My head is spinning.
These people, in their bright headscarves and dark suits, are the descendents of ancient Greece living, right here in front of me, in their ancient language.
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