Tens of thousands of people piled onto the streets of Berlin on Sunday to celebrate half a century of the European Union in the biggest outdoor festival the city has seen since the soccer World Cup.

As leaders from the European Union’s 27 nations thrashed out plans to reform the bloc’s institutions by 2009, live bands from across Europe wowed crowds by the Brandenburg Gate, one of Berlin’s best known symbols.

After dodging street performers on stilts and manoeuvring through the packed crowds, visitors could choose from national delicacies like fish and chips at the British tent, ice cream at the Italian stall or sangria at the Spanish.

Revellers had good reason to be cheerful at the 1.7-million-euro party, as clear blue skies matched the blue balloons and flags handed out to mark the 50th anniversary of the founding Treaty of Rome. But some were not sure whether there was much to celebrate.

“The party’s great. But it would be better if Europeans could be as united in reality as they are at this celebration,” said Anja Mehar, 34, a German saleswoman and mother of two.

“There are still so many cultural divisions. We are celebrating something we have not yet achieved,” she added. Others were happy to toast the advantages of the EU.

“What I like is the international aspect, the chance to learn other languages,” said 47-year-old gym teacher Thomas Van Den Berg from Gelsenkirchen, enjoying a glass of white wine.

“As a German, I think the creation of the EU was also a stroke of luck. But now it needs to become something more concrete,” he said, as his friends nodded and clinked glasses.

Berlin, long a symbol of Europe’s cold war division, was partly under Soviet domination 50 years ago. Sicilian magistrate Monica Ferraro, 39, said she believed the EU had had a positive influence on its 490 million citizens.

“There are several advantages, as a tourist in the EU, I don’t encounter so many obstacles. But I think a step forward would be a united language,” she said.

Not everyone in Berlin was ready to join in the party. Across the city, more than a thousand anti-globalisation activists, left-wing radicals and union members took part in a protest of the ceremonial summit. They were easily outnumbered by a 2,000-strong police force that tracked their demonstration.

“We are against plans for further market liberalisation and the militarisation of the powerful EU bloc. We want an EU of the people,” Mario Sperling of the Netzwerk Linke Opposition, one of the main initiators of the demonstration, told Reuters.