Even the reception at the entrance of the DITIB Merkez Mosque in the Marxloh district of Duisburg is rather unusual. Young women holding bottles of disinfectant welcome the visitors. "That's for our guests so they can clean their hands. Then they'll also be given some sweets," explains a friendly woman from the mosque. My hands now smell like lemon.

With room for 1,200 people, the mosque in Marxloh is one Germany's largest. The location once housed the cafeteria for a mining plant, but was opened turned into a house of prayer and a meeting place in 2008. In contrast to other German cities, the construction of a mosque in Marxloh was not accompanied by protests.

A place of dialogue

The mosque was chosen as an ideal location for the music-theater project "Urban Prayers" by Björn Bicker, staged by director Johan Simons as part of the Ruhrtriennale, an annual arts festival based in Germany's former industrial heartland, the Ruhr region.

The piece is about religious diversity in Germany and poses the fundamental question of what we all believe in. The project is being performed in six different houses of worship representing various religions.

Right from the start, Johan Simons insisted on including the Merkez Mosque. "At first, the piece was to be performed in a side room, not in the mosque itself. But the more we talked to people there, the more open-minded they became about it until, finally, they agreed."

Just the fact that songs are being sung in a mosque is anything but normal, says Nigar Yardim who works at the Merkez Mosque. "We have been involved in talks for two years, and we took a close look at what is being performed there," says Yardim.

Meeting each other with respect

All visitors must take off their shoes at the entrance to the elaborately decorated prayer room, before sitting down on a red carpet under a huge golden chandelier. The imam starts by reciting suras from the Quran. Five actors then ask questions in a monotonous, staccato style: "What do you believe who we are, what we believe, where we live?"

The project "Urban Prayers" focuses on topics like prayer, helping each other, compassion, dealing with crime and money, and also about different way of getting married.

The various themes are accompanied by the choir "ChorWerkRuhr," a professional vocal ensemble of the Ruhr region, which sings songs from different religious traditions. The choir's director, Florian Helgath, says settling on a particular Christian song was especially challenging. Finally, he opted for the "Kyrie" from Palestrina's "Missa Papae Marcelli."

"I thought about what would be representative for the Christian faith, while not being offensive to non-Christians, like the Last Supper or the crucifixion of Christ," says Helgath.

Speaking with many voices

It's hard to find a common denominator - and that also holds true for the actors and their roles. Are they speaking only for themselves, or for everyone? "Why do you think we carry beards, curls, hats, scarves? Why we ask you to keep your shoes on?" It's the so-called "choir of faithful citizens," inspired by the choirs in ancient Greek tragedies, that speaks in unison during the performance, commenting on the acts of the play. Yet the choir always speaks with different voices.

Playwright Björn Bicker has given a lot of thought to issues like migration and immigration. For his project "Urban Prayers," he visited Islamic, Hindu, Jewish and many other religious communities.

"In terms of art, I'm interested in a kind of exaggeration," said the author, explaining that this is the reason why the "choir of faithful citizens" never finds a common voice. "The choir keeps on permanently contradicting itself. That's what I find interesting, since that is a true image of our society."

These contradictions also point to meanders, commented Björn Bicker. During his research, he came across things that were not compatible with his concept of freedom and democracy. "But vilifying that, while talking about what's good, would not be constructive," he concluded.

"As soon as you get to know people, the world becomes more complex," said Bicker. Such conversations also formed the basis for his book "Was glaubt ihr denn" (What do you believe in?), which served as the basis for his theater piece.

The value of talking about doubts

The viewers never know which of the five actors is speaking for whom. Is he or she playing the role of a Christian, a Muslim or a Serbian-Orthodox Christian? Adding to the confusion is the fact that the actors, in terms of their looks, have various backgrounds, so they can't be put in a box based on appearances.

"What has fascinated me is that there are more questions than answers. That helps to see the world through the eyes of the others," says Nigar Yardim. But it's too bad that so few Turkish people attended the event, she adds. "The text is very difficult, so many Turks have a problem understanding [the German]."

Most of the 600 people in the audience are Germans. "Many of them have never visited a mosque before," says Johan Simons. Just that alone, in his view, is a big step forward in terms of a dialogue.

And in these times of mass migration, Islamist terrorism and right-wing populism, dialogue is important, he adds, since it can help us understand each other, while still remaining loyal to our views and values.

These values - freedom, equality and brotherhood - are what Johan Simons aims to question over and over again during the Ruhrtriennale, which runs through August 24.

The Dutchman said he still has doubts about his own values and those of others, even after participating in dialogue. "I originate from a European culture in which doubt is an important commodity. Especially nowadays, I have to show my doubts and talk about them. And that's what I'm doing."