By Mark Lowen
BBC News, Novi Sad, Serbia
Lily Allen is one of the stars of this year's festival
Step inside the imposing 17th-Century Petrovaradin Fortress in Novi Sad and you are greeted by a plastic yellow sign pointing left for Positive Vibration Reggae and right for Silent Disco.
For four days a year this peaceful idyll, perched high on the banks of the Danube, is transformed into a pulsating venue for southern Europe's largest music festival: Exit.
Now in its 10th year, this year's show is bigger than ever.
Almost 200,000 fans are descending on this sleepy Serbian town, cheering wildly at the main stage for Lily Allen and the Arctic Monkeys, or bopping away to the beats of local bands in the quaintly-named HappyNoviSad or Cafe del Danube arenas.
Each country has a certain number of official tickets assigned to it, so as to maintain a balanced national mix.
But it is hard to escape the hordes of British music-lovers, tents in tow, queuing up at the local grocery store for the necessary alcohol to tide them through the long all-night performances.
The festival is held each year in the Petrovaradin Fortress
"We have been really impressed by the Serbian people we've met," says Rob, offering me a swig of the apricot rakija liqueur he is sampling (which I politely refuse).
"I would probably never have come here had it not been for the festival. So it is a great way of experiencing a new culture."
As the bass booms across the dance arena, Belgrade student Jelena tells me she is never happier than at Exit.
"It's so unique," she shouts, trying to beat the cacophony. "This shows the world that we Serbs are fun, welcoming, loving people. How better to sell modern Serbia to the world?"
It is all a long way from the festival's humble beginnings back in the year 2000.
Exit has put Serbia firmly on the cultural map for young Europeans
Exit was born out of the street protests that accompanied the demise of the former Yugoslavia.
It was a spontaneous student uprising against the iron grip of then President Slobodan Milosevic.
The first event lasted 100 days, energising young people stifled under Milosevic's rule and urging them to go out and vote in the forthcoming election.
The slogan was "Exit out of 10 years of madness" - a clear reference to the political ambition of the event.
Festival founder Bojan Boskovic says it was a radical departure when it began.
"There was no arena for cultural or social expression. We were intimidated by the authorities. We never thought it would be held again the following year.
"But now it represents the very best of youth culture, 10 years on, not only of Serbia but of the whole Balkans," he adds.
The festival has always retained its political edge. Previous years have promoted a relaxation of the visa restrictions for Serbs or fought for sexual equality. This year, the theme is "green guerrillas," raising the profile of environmental concerns.
"We have a balance between politics, social issues and music," says Bojan Boskovic. "We will never lose that."
The performers are conscious of the festival's wider importance.
Nicky Wire, bassist with the UK band Manic Street Preachers, says Exit "gives you faith that music can be a symbol for change".
"That's what this festival seems to be. It projects Serbia in a pretty amazing way. Exit has almost become an ambassador for Serbia," he told me. "It's a different, deeper atmosphere to your usual festival. And that can only be a good thing."
Away from the festival Novi Sad is all charm and tranquillity
Away from the mud and hot dogs, the elegant Austro-Hungarian churches and cobbled streets of Novi Sad present a very different image.
Local residents are delighted that the festival has boosted the economy and brought tourists to a place not usually on their radar.
But Olivera Radovanovic, a former museum curator, says it is not all positive.
"The city authorities think the only cultural event in Novi Sad is Exit. It has a sort of monopoly over the budget.
"I am not happy that my taxes are spent on the rock festival. Local politicians must realise that there are other aspects to the cultural life of this city."
Some music fans are slumped in bright cushions in the Roots and Flowers area, a stone's throw from the ancient Petrovaradin clock tower.
The scene is a stark contrast between old and new, between the rich historical heritage of this country and a young, edgy population, shedding its war-torn past and eager to forge a new vibrant identity for itself. Exit is at the very heart of that.