I first came to this part of Bosnia 15 years ago. Back then, a ferocious war was being fought, Europe's most violent conflict since the defeat of the Nazis.
Bosnia was being torn apart - the three national groups who lived here each fighting for their own conflicting dreams of statehood and national liberation.
I've returned because I don't think the tensions that fuelled that war have been resolved. Bosnia is failing as a state - its three peoples, Muslims, Croats and Serbs, are still pulling away from each other.
At the centre of this region is a remarkable town, Medjugorje. It's remarkable because 29 years ago, on a steep, sun-baked hillside, six schoolchildren in what was then Yugoslavia reported that they'd seen the Virgin Mary and that she had spoken to them. That's the reason why so many pilgrims now come here.
They come from all over the world to climb the rocky hillside, often in bare feet, stopping to pray at intervals or to sing hymns. Groups of young men carry disabled pilgrims on stretchers to the place where the Virgin Mary is said to have appeared. Elderly nuns stride up the hill, holding their shoes and their rosaries in their hands.
The six children who saw the Virgin are now middle-aged. They have rock star status among the pilgrims. When they speak to the masses assembled here, pilgrims listen in on little headsets that provide simultaneous translation in a dozen or more languages. When they leave the stage, they are mobbed by the faithful.
Ivan Dragicevic was 16 at the time of the first apparition. He still sees the Virgin Mary every day and he invited me to witness one of the apparitions that takes place at precisely 6.40pm in the chapel he has built in his back garden.
A small group of pilgrims gathered and at precisely 6.40pm, after 40 minutes of prayer and Bible readings, Ivan got up from his seat, walked to the front of the chapel, kneeled down with his back to us, crossed himself and then, gazing directly ahead, began to move his lips.
He was muttering, inaudibly, sometimes nodding his head as though in agreement. After about seven or eight minutes he crossed himself again to indicate that the apparition was over and he turned to take questions from pilgrims about what the Virgin told him.
One asks about her appearance. Ivan tells her: "The beauty of Our Lady is very difficult to describe. Her eyes, her lips, her face. I'll tell you the most important thing. She has a grey dress, white veil, blue eyes, rosy cheeks, dark hair. She has a crown of stars and she floats on a cloud, never touching the ground."
I asked what language she used to communicate with him. "Our Lady speaks in Croatian," Ivan revealed.
Some in the Catholic Church are sceptical about these apparitions. The Vatican does not recognise the Medjugorje apparitions and that is the line church leaders in the Bosnian capital, Sarajevo take too. Marto Zovkic is archbishop of Sarajevo. He was a member of a Vatican Commission of Inquiry set up to examine the Medjugorje phenomenon.
"I was not very convinced that the events are somehow spontaneous, natural," he says.
Once a month, the parish asks for guidance. The archbishop says he was there on one occasion, when the woman who experienced the apparition and should have asked for guidance, admitted that she had forgotten to do so.
The pastor, he says, gave the woman a paper with a written text, asking her to go back into her trance and "ask Our Lady, could this be the programme for the next month?"
A minute or so later the woman delivered the answer: "Yes, Our Lady confirms that this is the programme for the coming month."
But in Medjugorje, no-one has a shred of doubt.
The apparitions have made what was once an unremarkable and impoverished mountain village prosperous. You can buy a piece of Virgin Mary memorabilia in plastic. Have it blessed by a Medjugorje priest and you take a piece of the miracle home with you - its value, to the faithful, limitless.
And everywhere, mingled with the Christian imagery, are the symbols of Croatian national identity. Flags, football jerseys, jewellery, umbrellas, caps, walking canes. For here, religion and national identity are inseparable. Being a Catholic is what defines you as a Bosnian Croat. The Catholic Church - through the decades of Communism - became a way to assert an otherwise suppressed Croatian national sentiment.
Father Tomislav, a Franciscan monk, accepted the truth of the apparitions straight away. For him, the miracle chimed with a very secular, very political aspiration - the deliverance of the Croatian people from what he saw as foreign domination.
He described the effect that the first apparition had on local people: "We were asking for freedom - praying for freedom here - freedom of speech, freedom of movement, even our religion and that was for us a sign of release after centuries and centuries of enslavement. It was like a response to our prayers that Heaven should give the people a sign that they are not forgotten."
Bosnia is usually thought of as a predominantly Muslim country. In fact it's not. Most of its people are Christian - Orthodox Serbs mostly in the north and east, Catholic Croats mostly in central and western parts. In the war that tore this place apart not long ago, many (though by no means all) Serbs and Croats fought to dismember the country called Bosnia-Hercegovina. They didn't want to be part of it, they believed it had no legitimacy. They did not want to share statehood with their Muslim neighbours.
The Bosnian war gave to the lexicon of conflict a grim new euphemism: ethnic cleansing. In much of this part of Hercegovina, Croatian nationalists seized control and drove their former Muslim neighbours out.
I came to Medjugorje during the war. Then, the place was full of young men in military uniform, fresh from the frontlines, tired, drawn, taciturn. In my mind's eye I could still see them after all this time, in the spaces where the pilgrims are now.
Some who fought cling to the dream of separation from Bosnia even now - the dream of a separate Croatian ethnic state here - even if the cost is a return to war. "We have the right to start a war - it is our right," Petar Milic a nationalist member of parliament, told me.
"What we're doing now is waiting to see if the politics will bring results in getting our own republic. If not, we might take unilateral action - whether that would be a war or revolution, that's something else. But we certainly have the right to self defence."
I asked him about the potential for Medjugorje to become a rallying point for such Croatian national aspiration. "Hopefully in the future it might become a place where we can absorb the spiritual energy to help us achieve our goal," he said.
In the evening, as the sun dips below the horizon, a torch-lit procession snakes through the heart of Medjugorje, brimming over with something resembling religious ecstasy. Many of the pilgrims are carrying their national flags.
When you first see it, it looks like a tremendous celebration of immense diversity and unison - there are flags from all over the world, French, Spanish, Portuguese, there's a Polish one, there's a South Korean one, a Brazilian one and, of course, dozens and dozens of Croatian ones.
And it's only after a while that you realise that there's one flag that's very striking by its complete absence and that's the flag of the country we're actually in - there's not a single symbol anywhere in this crowd of Bosnian national identity. There's nobody here whose primary national allegiance is to the country that we're actually in - and that is troubling.
Many local Croats fought, not long ago, to dismember Bosnia-Hercegovina. They nearly succeeded. But an internationally brokered peace plan placed them in a state shared with Muslims and Serbs - their former enemies.
For millions around the world Medjugorje is place of pilgrimage. But it stands here amid the mountains as a shining symbol of Croatian national aspiration on the territory of Bosnia-Hercegovina, its people not yet reconciled to their place on this side of the border, or to a future shared with their Muslim and Serb neighbours.