By Julia Buckley, CNN
Wherever you go, the experience is usually the same.
You enter a church or a cathedral, and an ecclesiastical hush descends. You admire the architecture, the artworks, the centuries of history and of faith that have stood the test of time.
And then you enter a special chapel or museum, where the holiest of items resides. Behind a glass case stands the stuff of legend: the Holy Grail.
Or is it? What makes this cup the Holy Grail - but not another?
In Europe alone, there are said to be around 200 cups, each thought to be the Holy Grail - the cup used by Jesus Christ at the Last Supper.
Believers flock to see them and pray over them. But which is the real Grail - and does it even exist?
A religious or cultural reality?
One thing's for certain - the Holy Grail is embedded deep into our collective imagination.
The idea of a quest is a constant theme in literature, art and movies, while we routinely refer to what would be our ultimate goals - but usually lie tantalisingly out of sight - as the "holy grail".
Major medical breakthroughs are often called the "holy grail" for the disease in question.
It's part of pop culture, too. Dan Brown made millions off his interpretation of the Holy Grail in the Da Vinci Code, in which he posited that the Holy Grail was not an object, but a secret - that Jesus Christ had fathered children with Mary Magdalene.
And who can forget Harrison Ford reaching out for the cup of a carpenter in Indiana Jones and the Last Crusade?
"I honestly do not think that the actual cup from the Last Supper still exists," she said.
"Jesus certainly used a cup at the Last Supper, but if you look at some Gospel accounts, the room was already prepared by someone else [before they arrived]. So it may not have been his cup."
For Pierce, a Catholic, the idea of the Holy Grail is more symbolic than realistic - in her words, "a cultural reality rather than a religious reality."
But for many people, the Holy Grail is a real object - and one that it's possible to see if you go to Valencia. Or Léon. Or Genoa. Or any of the many places where tradition claims it resides.
You might even be able to feel the mystical power of the Holy Grail if you visit one of the many places it is said to be hiding, just out of site. Up the mountain of Montserrat, outside Barcelona, for example. Or in the Polish countryside, where the shadowy Knights Templar might have hidden it. Or around Glastonbury Tor, the mysterious hill in southern England where, medieval legend declared, Joseph of Arimathea brought the Holy Grail shortly after Jesus' death.
At Valencia, in eastern Spain, enter the cathedral, and to the right is a chapel, built expressly to house the Santo Cáliz or Holy Chalice.
"Tradition reveals that it is the same cup that the Lord used at the Last Supper for the institution of the Eucharist," reads the cathedral's website about the "Holy Chalice of the Lord's Supper."
They believe that St Peter took it to Rome, from where it was sent to Spain in the third century AD.
Valencia's tourist board website also describes the cup as "the Holy Chalice… used by Jesus Christ at the Last Supper."
Announcing that you have the Holy Grail is, of course, a tourism draw. It has been since the medieval period, when Europeans taking part in the Crusades would bring back relics from Jerusalem.
From worship to tourism
In fact, relics have been central to Christianity since the start, said Pierce.
When early Christians were martyred, other believers would pray at their graves.
"The martyr acted as a patron or intercessory for their prayers to be lifted up to heaven" - a practice taken from ancient Rome, where the "patronage system was an important part of society."
That idea of saints intensifying prayer, or flagging it to the right place, persists in Christianity today.
But it wasn't just the graves of martyrs that became holy; it was anything to do with their body, or things they had touched.
"Objects they might have handled were considered to have that same grace - a connection with the holy," said Pierce.
Of course, the cup held by Jesus with which he showed the disciples how to perform the eucharist, on the table as he announced that he was soon to be betrayed, would be the holiest of holy objects.
Little wonder that so much effort has gone into finding it.
During the time of the Crusades, interest in Jesus' life on Earth increased, said Pierce.
People were "going back and forth" between Europe and the Holy Land, looking for artifacts that could have been related.
That's why most of the supposed Holy Grails around Europe first arrived on the continent during those centuries.
"It's similar to the interest in the paranormal we have now," said Mathew Schmalz, founding editor of the Journal of Global Catholicism and professor of religious studies at Holy Cross.
"In the Middle Ages, it reached a public consciousness that it didn't have before."
But over the centuries, collecting relics hasn't purely been about getting closer to God, said Schmalz. There were "various economic interests related to pilgrimage," he said.
"Relics were taken away from tombs and widely dispersed. You have a variety of places becoming pilgrimage sites which was a very lucrative business for those who had the relics."
Religious tourists would make pilgrimages to these places, boosting the local economy as they did so.
Relics were also political at the time of the Crusades.
"Finding items like the lance that pierced the side of Christ was considered affirmation of the divine mission to 'liberate' the Holy Land," said Schmalz.
That's one of the reasons that some "relics" are so numerous that they couldn't possibly be true.
"You could construct a city with the wood that's claimed to be the true cross," he said.
Jesus or... King Arthur?
The Holy Grail may have started as a sacred relic for Christians, but over the centuries, it has also come to have relevance to others.
For starters, it has been linked to the legendary King Arthur since the Medieval period - thanks to chivalric poetry, said Pierce.
A ninth-century French poem posited that Joseph of Arimathea had caught the blood of Christ in the Grail during the crucifixion and had later taken it to Glastonbury in what's now England.
"This was conflated with Celtic, Irish, Welsh and pre-Christian narratives about objects imbued with power," she said.
A "graal" or grail in English originally referred to a deep dish, serving platter or even a cauldron belonging to early British kings, according to ancient myth.
In the 12th century, Chrétien de Troyes' poem Perceval, the Story of the Grail is a romp including King Arthur and the Knights of the Round Table, a chivalrous quest, a bloody lance - and a glittering grail, a serving dish with magical healing powers.
By the 15th century, Perceval had become Galahad, the son of Arthurian knight Lancelot, who goes on a quest for the grail, finds it, and chooses to die on the way back after a heavenly vision.
Galahad, by the way, was able to heal the sick and perform miracles.
Sound familiar?
How one woman 'found' the Holy Grail
So what is it like to have a Holy Grail in your city? Representatives from the Cathedral of Valencia didn't reply to requests for comment from CNN.
Neither did anyone from the Italian cathedral of Genoa - home to the Sacro Catino, a beautiful glass bowl, once thought to have been the Holy Grail, made of emerald, but now seen as more likely to be crystal, and work of Islamic art from the 9th or 10th century, brought to Italy in the 11th.
But someone who is convinced she has the grail in her hometown is Margarita Torres Sevilla, a professor of medieval history at the University of Léon in Spain.
In fact, Torres was the one to discover that what was thought of as a mere medieval chalice in her city was - she believes - the Holy Grail.
In 2010, she and colleague José Miguel Ortega del Río were working at the Basilica of San Isidoro, a church in Léon that doubles as the burial place for the royal dynasty of Léon and Castile. They were looking at items in the Basilica's Museum of Medieval History.
"Some objects came from Islamic countries but didn't have the correct references," she said.
Among them was the Chalice of Doña Urraca - an onyx chalice that had been adorned in a gold casing and encrusted with precious jewels.
It had come to Spain from Egypt in the medieval period, apparently as a diplomatic present.
Torres and Ortega del Río delved deeper into its provenance, asking a colleague in Cairo to look for documents that could explain this gift to the Spanish.
What they found astonished them.
"In the middle of the 11th century, there was a great famine in Egypt and the caliph had asked for help from other Islamic countries," she said.
In the library of Cairo's Al-Azhar University were two medieval parchments from the 14th century. One, an apparently historical account - recounted that the taifa (ruler) of Dénia had sent a boat full of food to Egypt.
Dénia, near modern Valencia, was under Muslim rule at the time.
The parchment goes on to say that in return for the help, the taifa made a request for "the cup that the Christians call the Cup of the Messiah… used during the celebration with his disciples".
The cup had been found in "one of the small churches that are on the outskirts of Jerusalem" and possessed "extraordinary medicinal powers" according to Christians, said the document - which also gave the caveat that "men of science and doctrine disregard it."
Ali bnu Muyahid ad-Danii, the ruler of Denia, requested it so that he could "send to the King of Léon … to strengthen their alliance," the document continued.
The previous year, Léon had attacked Valencia - the war was getting too close to comfort for those in Dénia, and it appeared that the taifa wanted to placate Ferdinand I, the king of Léon.
Ferdinand suffered from "the disease of the stones" and the taifa thought the miraculous cup might help.
The other parchment, also from the 14th century, purports to be a copy of a letter from Salah ad-Din Yusuf ibn Ayyub (known as Saladin), the 12th-century sultan of Egypt and Syria.
The letter recounted how he had asked to be sent the "fine shard" of the "holy stone" or "cup" that had been chipped off during its journey to Dénia, for his sick daughter.
She was healed by the "piece of stone placed upon her body," and the shard had been kept carefully in the Islamic public treasury, states the document.
They went back to the cup in the church in Léon.
"We checked - it had a cut in it, as the parchment suggested," said Torres. "We knew we had a hot potato in our hands."
The pair claim to have dated the onyx cup to the first century, and believe that Doña (princess) Urraca, Ferdinand's daughter, melted down all her jewellery to cover the chalice in riches.
They've even identified what they think is the onyx cup in a painting of the Last Supper at San Isidoro's royal pantheon, where the dynasty is buried.
They believe that is a hint about the cup's identity. Of course, not everybody believes them.
One Oxford professor memorably said it was "idiotic" to claim that the cup must have belonged to Jesus, even if it's of Roman origin.
Torres - proving that the Grail has penetrated culture like no other - likens her situation to that of Hollywood's Indiana Jones taking his leap of faith before finding the Holy Grail.
"He closes his eyes and starts with a step. Our sensation was the same," she said.
"I'm a Christian, but my colleague is not. My mother was a historian; his father was a journalist."
They were not the type to get carried away, she said.
The idea that a princess would have donated her jewellery to cover a broken cup in gold is, she said, "like the daughter of Bill Gates melting down her jewellery to cover a broken toy."
Torres' claims are certainly persuasive - and although she was Léon's city councillor for tourism from 2015 to 2019, she said she "put a line between being a politician and a historian."
Can she guarantee it's the cup of Christ?
"I can offer that the cup venerated in Jerusalem from the fourth century to the 11th century is the same as you see in the chalice of Urraca," she said.
"But I'm not sure what happened from the first to the fourth century, because I was not in Jerusalem, not with Jesus Christ, and neither were you."
'My faith doesn't depend on this'
For Pierce, who doesn't believe that the Grail exists anymore, items like the chalice of Urraca are still worthwhile as a cultural phenomenon.
"I'm very sceptical … but what's important is the fact that these items were venerated - they're literary objects and cultural reality," she said.
"My faith doesn't depend on [this]. To believe in Jesus Christ doesn't necessarily mean that there are actual physical remnants of his [life]."
She compares the quest for the Holy Grail to the Shroud of Turin.
"I've seen it, it was fascinating, but analysis shows it's from a later period.
"That doesn't threaten my belief in the death and resurrection of Jesus Christ at all - someone believed in it so much that they fabricated it," she said.
Schmalz, who is "doubtful" about whether the Grail still exists, agrees.
Not that he's against all relics. He used to wear a piece of Pope John XXIII's vestment around his neck.
"I mysteriously lost it and many people said it was the result of a demonic attack," he said.
"I believe it was more a result of my carelessness. But I do believe relics are important - they connect us not just with holy people but with God."
His best bet about what the Holy Grail would look like if it existed?
"I'd agree with the Indiana Jones vision of it as a simple cup. The 'cup of a carpenter' who was at a local inn.
"In some ways, that's the religious meaning - that something so simple and worldly could hold the blood of Christ."
Is that the Holy Grail sitting in Léon? Or Valencia? Or any of the other 200 places that claim to be home to it? We'll never know.
But one thing is for sure. The idea of that simple cup of a carpenter looks set to stay in the public consciousness for another 2000 years.
- CNN