Exactly 60 years ago, the rain was pouring down on Rome. This morning there isn't a cloud in the sky; a good omen on a tricky day.
In the great hall of Michelangelo's Palazzo dei Conservatori the leaders of 27 nations have gathered to mark the anniversary of a union that began with just six countries.
But how do you celebrate your birthday and present a positive vision of Europe when the fabric is fraying? How do you renew your vows when you're about to go through a messy divorce?
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On 25 March, 1957, the leaders of six countries realised a dream. Belgium, France, Italy, Luxembourg, the Netherlands and West Germany put their names to a bold experiment: the European Economic Community (EEC).
The club now comprises so many more countries and has presided over the longest period of peace in the continent's history. That's the nostalgic reflection the leaders gathered here are focusing on.
They have to, because the future looks very uncertain.
The voices questioning the point and legitimacy of the Union are stronger than ever; nationalism is rising; the wealth gap across member nations is huge; migration pressures are fundamentally changing the political landscape and one of the club's most integral members has just quit.
The decision of the British people to leave the EU was both a surprise and a body blow for the rest of the Union. The establishment governments who run Europe didn't expect it and they didn't want it.
"A failure and a tragedy" is how EU Commission President Jean-Claude Juncker characterises it.
Britain is not here for the celebrations; an appropriate absence given Brexit - the UK could hardly be celebrating the achievements and prospects of a club it voted to leave.
Article 50, the formal notification that the UK is leaving, will be triggered on Wednesday.
Increasingly from the rest of the club there will be a drive to present Brexit as just one of many priorities and not the main one. The German and French elections are more important in Europe. Then there's the ongoing migrant crisis and the bubbling financial crisis.
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It's much easier for the leaders to focus on nostalgia than to present a plan ahead, because they don't have one.
They have lots of ideas but no unified plan.
Curiously when they signed the original Rome Treaty 60 years ago there was no plan either; not on paper at least.
A series of unfortunate errors culminated in the leaders signing a document which only had the first and last page printed. The bundle in the middle were blank.
A train bringing the documents from Brussels to Rome had been blocked from passing through Switzerland. The documents were hastily reprinted in Rome but overnight cleaners then threw the lot in the bin.