By Malcolm Billings
BBC, southern Spain
In southern Spain, once the centre of an Islamic civilisation in Europe, the Muslim community has appealed to the Vatican to be allowed to pray alongside Christians in what was once the Great Mosque of Cordoba.
Although a cathedral, the building is known as "La Mezquita", or mosque
It is one of the oldest buildings in the Islamic world and one of the most beautiful.
The first thing I saw was a courtyard full of orange blossom. A fountain played in the middle.
I felt that I was already back in the Middle Ages making my way towards the entrance of the mosque itself.
The interior is stunning - a symmetrical forest of marble pillars supporting hundreds of graceful arches made of pink bricks.
Many of the marble pillars have a curiously Roman look about them.
Not really surprising. They were almost certainly dug out of a ruined Roman temple that still lies under the mosque.
The buildings under the mosque were used as a quarry and the best decorated bits and pieces fell neatly into place as the mosque took shape more than 1,200 years ago.
The Great Mosque became the spiritual heart of Cordoba when the city, with a population of about half a million, was the biggest and wealthiest in Europe.
The Muslim rulers of southern Spain had created an important cultural centre with a flourishing society made up of Jews, Christians and Arabs.
Appeal to Vatican
I made my way through the arches to the prayer niche, the Mihrab, which was added in the 10th Century, when Christian craftsmen from Constantinople were imported to decorate it with gold, red, green and turquoise coloured tiles.
The 1,000-year-old inscriptions in Arabic praising Allah are still there in this sacred area where Muslims hope to be allowed to pray. They have appealed to the Vatican to be allowed to do so.
The 500 or so Muslims now living in Cordoba have outgrown the small building given to them for prayers in one of the city's parks.
Standing by the prayer wall and facing Mecca I asked a cathedral guide what would happen if a Muslim fell to his knees and began to pray.
"Cathedral security would be here immediately. It's not allowed", she said. "This is cathedral, not a mosque."
And that is the moment when a visitor confronts modern reality.
The Great Mosque was turned into a church when Cordoba fell to the Christians in 1236. Its arcades were filled in to become chapels and shrines, and an altar was erected in one of the mosque's central aisles.
For almost 300 years Christians worshipped in this curious makeshift cathedral, but in 1523 the pressure to replace the mosque built up in a militant society that had banished both Jews and Arabs.
The cathedral chapter got permission to build. But what happened is remarkable.
Muslims are not allowed to pray inside the Great Mosque
In other cities like Seville, as the re-conquest squeezed the Muslims out, mosques were demolished and churches covered the sites.
In this case, a new cathedral was built inside the mosque.
It is a shock which visitors today are rarely prepared for. Carved out of the centre of the building, using perhaps 20-25 per cent of the mosque's floor space, is a Renaissance church that could be one of a dozen small churches in Rome.
Marble walls and domes, gilded statues of Christ and the saints, and choir stalls superbly carved in mahogany won from the forests of Spain's new South American colonies, were erected.
They had built the smallest cathedral in Spain in the middle of the largest mosque. Even then the decision was controversial - the town council was against it and Charles V, who sanctioned the project, seemed to regret the intrusion after the deed was done.
Archaeologist Isobel Martinez Richter believes that ''people then must have thought of the mosque as a symbol of tolerance and that the decision not to demolish it was ''a sign of respect for the multicultural history of the city".
"The group who engineered this solution'', she added, ''must have been very wise - I only wish we knew their names."
Spaniards still take pride in their multicultural roots. The wave of immigration from Morocco to fill the jobs created by a booming economy has created few problems.
But since 9/11 and the terrorist attacks in Madrid, can that tolerance be sustained?
The attacks profoundly shocked Spaniards, many of whom are bewildered by the way Muslim fundamentalism has targeted Spain.
Fear and suspicion of Muslims have become part of everyday life. It is hardly a propitious time for discussion about Muslim prayers in Cordoba's cathedral, but local politicians have not ruled it out. Now is not the time though to debate the issue, they say.
Isabel Romero, a Spanish convert to Islam, told a local paper that being allowed to pray in the cathedral is not about claiming anything and much less about re-conquering.
"It does not make sense", she said, "that when Muslims go to pray they are told to get up."
Southern Spain has many superb Islamic buildings from the past - the Alhambra palace at Granada is one of the best known. In Seville the city's great landmark is the massive minaret of the 12th century mosque.
Cordoba's mosque however is a unique survival - saved only because of a decision in the sixteenth century to insert a Renaissance cathedral in the middle of the building.
Perhaps Friday prayers may once again be heard in one of the finest buildings on the list of World Heritage sites.
From Our Own Correspondent was broadcast on Saturday, 1 May, 2004 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.