Protesters have clashed with police on the eve of a global summit on climate change in Paris.
French president François Hollande has described their actions as scandalous in the wake of this month's terror attacks in the French capital.
Loud bangs, smoke, and tear gas filled the Place de la République as police clashed with anarchist protestors, with President Hollande quick to respond.
"This is why demonstrations were not authorised - we knew there would be troublemakers who have nothing to do with environment activists or with those who want the conference to be a success and are only there to create incidents," Mr Hollande said.
But most people did not want to make trouble - only a statement - which they did by leaving shoes in the square. Even Pope Francis had a pair laid on his behalf.
"What we are seeing here is an outpouring of determination of Parisians to be heard nonetheless," said Emma Ruby-Sachs, of the Avaaz climate campaign group. "These are shoes from the closets of average citizens decorated with notes from people."
People formed a human chain around the route the march had been due to take.
The conference venue itself in Le Bourget is just 7 kilometres from the Stade de France - the scene of the first explosion in the terror attacks two weeks ago.
And it's even closer to the St Denis apartments where the alleged mastermind was killed in police raids.
With two suspects involved in those attacks still on the run, authorities have posted more than 15,000 police to patrol the area around the site.
Climate change marches also took place in other cities around the world, with an estimated 50,000 attending in London, including many famous faces.
There does appear to be political momentum to reach some kind of meaningful agreement to tackle global warming, though the risk is it's overshadowed by groups with another agenda.