In an apparent reference to the famed Avignon theatre festival, he also singled out "cultural events that take place in the South of France in which thousands of Christians gather for a month".
"The main walkways become black with people and a simple grenade can injure dozens of people, not to mention a booby trapped device," he said.
His contact then asked him to travel with a fellow would-be terrorist to Algeria to "benefit from a military training and training in combat techniques".
After that, he would return to France, stake out targets and "await your instructions".
"I am fully ready and prepared," he replied.
Although the plans were at the discussion stage, French police arrested the Algerian in June last year, a month before he was due to fly to Tunisia and then on to Algeria.
Daphne Pugliesi, his lawyer, said he had been brainwashed, telling Le Parisien: "The arrest was a relief for him."
The revelations came as Bernard Cazeneuve, France's interior minister, unveiled tougher anti-terrorist laws, including proposals to ban a suspect from leaving the country if it is thought he intends to fight jihad abroad, such as in Iraq or Syria.
Last month, police arrested Mehdi Nemmouche, a French jihadist who fought in Syria, and allegedly killed four people at the Brussels Jewish Museum in May after travelling back to Europe.
The legislation, to be presented to parliament "in the coming days", will also create powers to force internet providers to block Islamist hate propaganda and also allow investigators to use pseudonyms to go undercover in pro-jihadist sites.
Some 800 French nationals or residents are thought to have left to fight in Syria since the start of the civil war.
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