Today's European Union is the product of efforts led by France and Germany in the wake of World War II to bring peace to a continent that had seen centuries of war.
But the political and economic union ushered in by the March 1957 Treaty of Rome that leaders will celebrate this week is in many ways less united than ever.
Divisions abound over migration, populism and the economy, combined with worries about its place in the world and life after Brexit.
While the mantra of EU founding father Jean Monnet was that Europe would be forged in crisis, fears are now that it may be fatally weakened.
"This mantra, you couldn't hear it any more during the last years in the Brussels bubble," said Stefan Lehne, visiting solar at Carnegie Europe.
"There is not just one big crisis but a multiplicity of very severe and complicated challenges, and I think this changes things," Lehne told AFP.
Lehne said it was more likely the EU would eventually cease to be in its current form, becoming an "ever looser union" instead of an ever closer one, as the EU's treaties famously envisaged.
President of the European Parliament Antonio Tajani. Source: EPA
'Holy Roman Empire'
"I think sometimes of the Holy Roman Empire that continued to exist for hundreds of years after it had sort of died politically," he added.
In Rome on Saturday, EU leaders are set to endorse a "multispeed" Europe that allows some countries to push ahead with cooperation while others lag behind, but which some call a slow disintegration.
After years of burying their heads in the sand, European leaders have finally acknowledged they face an existential crisis.
New European Parliament chief Antonio Tajani said this week that the "European project has never seemed so far away from the people as it does today".
But what makes today's crises different from those that the organisation formerly known as the European Economic Community faced in its early years?
In the 1960s there was the 'empty chair crisis' when France under General de Gaulle blocked decision making, and de Gaulle's repeated 'non' to Britain joining.
Then the oil crisis in the 1970s and repeated referendums on the treaties all posed major challenges.
Still, Europe managed to emerge triumphant from the Cold War and then rapidly expanded in the early 2000s.
It has also pushed through with major projects like the euro and the Schengen passport-free area -- but increasingly tensions over these big achievements are what is driving the EU apart.
"The crises we face today fundamentally call into question the point of the European project," said Frederic Allemand of Luxembourg University.
"Clearly peace is still the frontispiece, but apart from that, what kind of social and economic model do we want in Europe?"
Opposed to UK joining the EU: Former French President Charles De Gaulle. Source: Bettmann
'Muddling through'
The last decade has in particular brought one setback after another.
Following the 2007-8 financial crisis, growth has remained sluggish and unemployment high. The eurozone debt crisis almost forced Greece out and German-led austerity has caused a legacy of bitterness.
Europe has also failed to halt the carnage in Syria and the conflict in Ukraine, both sources of tension with Russia, while a series of Islamist terror attacks have transformed the security environment.
A wave of 1.4 million asylum seekers in 2015 and 2016, largely sparked by the Syria war, has meanwhile shattered the EU's facade of solidarity as Eastern Europe blamed Germany's open-door policy for the influx.
"Never before have I seen such fragmentation and also such little convergence in our union," European Commission chief Jean-Claude Juncker said last year.
Many in Brussels hope that unity in the face of Brexit negotiations, and clarity after key elections in France and Germany, will help to focus minds by the end of 2017.
But they are already divided over what comes next.
Some want to push ahead with defence, especially amid insecurity over new US President Donald Trump's commitment, or the economy, while others in the former Soviet east want to ease off on integration.
But most will still want to keep the advances that the last 60 years have brought, said Hendrik Vos, a professor at the University of Ghent.
"It is not the most efficient and not the most beautiful way to escape from a swamp -- but you can escape a swamp by muddling through and that's the way the EU operates," he said.
Refugees approach the German border during a snow shower at the German-Austrian border. Source: DPA
Key moments
1951: Belgium, West Germany, Luxembourg, Italy and the Netherlands sign Treaty of Paris establishing the European Coal and Steel Community (ECSC). The treaty expired in 2002.
1957: Treaties of Rome are signed, establishing the European Atomic Energy Community (EURATOM) and the European Economic Community (EEC). The treaties came into effect in 1958.
1963: Charles de Gaulle blocks UK attempt to join the EEC.
1967: Charles de Gaulle blocks UK's second attempt to join the EEC.
1973: Treaty of Accession brings UK, Ireland and Demark into EEC.
1979: European Monetary System, including the Exchange Rate Mechanism, is established.
1986: Single European Act is signed, coming into force in 1987. By this time, Greece, Spain and Portugal are all also members of the EEC.
1990: West and East Germany reunify, bringing East Germany into the EEC.
1992: 'Black Wednesday' sees UK and Italy forced out of the Exchange Rate Mechanism after nearly £4 billion was spent attempting to sustain value of the sterling.
1999: Creation of the euro.
2007: EU member states sign the Treaty of Lisbon, streamlining the organisational strucutre of the EU and establishing a full time president and foreign minister for the union. The treaty came into force in 2009.
2012: European Union wins Novel Peace Prize for “over six decades contributed to the advancement of peace and reconciliation, democracy and human rights in Europe".
2016: UK holds referendum in June on whether to remain in or leave the European Union. Leave won by 51.9 per cent to 48.1 per cent.
2017: Prime Minister Theresa May moves to trigger Article 50 of the Lisbon Treaty which would see the UK formally leave the EU by 2019.
