At first, when you come out of the metro station on the Place de la RΘpublique, you feel as if you're at a party. The sun is shining and the chestnut trees are in blossom. Rap music blares from amplifiers on a truck bed.
A girl with orange and purple plaited hair holds a placard saying, "Let's save the Republic". Another young woman sits astride a man's shoulders, like the blonde model who became the icon of the May 1968 rebellion.
She brandishes a sign saying "Shame" on one side, and "1936 No Pasaran" on the other. "Vote for the crook, not the fascist", is a popular slogan. The "crook" is President Jacques Chirac; the "fascist", his challenger in the May 5th election, is the extreme right-wing leader Mr Jean-Marie Le Pen.
For two days, all over the country, tens of thousands - hundreds of thousands by some estimates - of young people have taken to the streets to protest at Mr Le Pen's presence on the ballot. They make self-conscious parallels with the Spanish Civil War and other high moments of revolutionary history. A new generation is learning that favourite French pastime: demonstrating.
But beyond the gaiety and colours, beyond the fraternity that stirs such gatherings, there's a strong sense of crisis and an uncertain future.
"We're at a turning point; France is changing," says Mr Denis Paget, the secretary general of the teachers' union SNES, whose leadership yesterday marched with the lycΘe students. Not since Mr Francois Mitterrand was elected in 1981, Mr Paget said, had he felt his country collide with history.
As the cortege moved towards the Bastille, the cracks in the anti-Le Pen movement became apparent. Julien and Paul, both 16, hold dual French-Israeli nationality and are members of Betar, the militia-like youth movement of the Likud party. Both wore Israeli army dog-tags. "The French have always been anti-Semitic," said Julien. His grandmother, from eastern Europe, survived the pogroms.
"She says it started like this - burning synagogues, people throwing stones." But recent attacks on Jews in France were carried out by young north Africans, not the extreme right. Yes, said Julien.
Some of his friends advocated voting for Mr Le Pen, "because he would take care of the Arabs".
Paul interrupted. "Look, there's a guy with a keffiyeh. For us that's a symbol of terrorism. We can't beat him up, because we're out-numbered."
The young man wearing the keffiyeh [Bedouin Arab head-dress] was Boudjemah, 19. He'd seen the two Israelis at other demonstrations, where there was violence.
"I'm for the oppressed; I would have been a Jew in the Second World War," Boudjemah said. "Today, I'm a Palestinian."
Boudjemah's greatest fear was that "people will vote massively for Chirac, and he's a fascist who doesn't say so". As a member of the Revolutionary Communist Youth, Boudjemah believed the only solution was "mobilisation in the street".
The red T-shirts he gave away proclaimed: "Resistance!" The black T-shirt he wore said: "Let's Break the Nazis" and the pamphlet he handed me said: "Crush the National Front."
A few casseurs (literally, "breakers") tagged alongside the procession, recognisable by their track suits and running shoes.
Most of the shops had pulled down their metal shutters, out of fear of the casseurs and the riot police who'd charged them in the early hours of the morning.
"I hope they won't fight again tonight," said 93-year-old Germaine, who was taking her afternoon stroll with a cane.
"I've lived through four revolutions," she boasted. "1934 was really something." Why does France keep having revolutions? I asked her. "Because we're badly governed," she replied.
The CRS riot police who followed at the back agreed with Germaine. "This has got to stop," said a blue-uniformed, grey-haired cop armed with a pistol and night-stick.
The CRS in front of him carried plexi-glass shields and tear gas launchers.
"They're bad eggs," he continued, gesturing towards the teenagers. "The whole lot of them. I'm voting for Le Pen. So is every policeman in this country. Why should they be allowed to do this? Le Pen's a politician like any other; he has a right to stand for office."