French President Francois Hollande and German Chancellor Angela Merkel have marked 100 years since the Battle of Verdun.
The 10-month battle between February and December 1916 - the longest in the First World War - killed 163,000 French and 143,000 German soldiers. It wounded hundreds of thousands of others.
The frontline villages destroyed in the fighting were never rebuilt and the battlefield zone still holds millions of unexploded shells, making the area so dangerous housing and farming are still forbidden.
With no survivors remaining, Sunday's commemorations were focused on educating youth about the horrors and consequences of the war.
Some 4,000 French and German children were taking part in the day's events, which conclude at a mass grave where, in 1984, then-French president Francois Mitterrand took then-German chancellor Helmut Kohl's hand in a breakthrough moment of friendship and trust by long-time enemy nations.
"Verdun is more than the name of your town - Verdun is also one of the most terrible battles humanity has experienced," Mrs Merkel said in a speech at city hall, calling Mr Hollande's invitation to join the centenary "a great honour".
"We are all called upon to keep awake the memory (of Verdun) in the future, because only those who know the past can draw lessons from it," the German leader said.
Mr Hollande praised the city of Verdun as "the capital of peace".
"Verdun is a city that represents - at the same time - the worst, where Europe got lost, and the best, a city being able to commit and unite for peace and French-German friendship," he said.
Mrs Merkel said the commemorations show "how good relations between Germany and France are today" and the achievements of European unity.
Mr Hollande and Mrs Merkel were spending all of Sunday together.
In the morning, Mr Hollande welcomed his German counterpart under heavy rain at the German cemetery of Consenvoye, near Verdun, where 11,148 German soldiers are buried.
They laid a wreath, accompanied by four German and French children, and walked side by side for a few minutes in the cemetery, sharing an umbrella.
After lunch, they visited the newly-renovated Verdun Memorial.
The museum, which reopened in February, immerses visitors in the "hell of Verdun" through soldiers' belongings, documents and photos, and from its new rooftop they can observe the battlefield.
The main ceremony took place in the afternoon at the Douaumont Ossuary, a memorial to 130,000 unidentified French and German soldiers.
The ceremony conceived by German filmmaker Volker Schloendorff included children re-enacting battlefield scenes to the sound of drums amid thousands of white crosses marking the graves.