Notre Dame was originally planned, but complications arose with it.
Viewers watching the opening ceremony of the Olympic Games in Paris saw a reference to the Assassin’s Creed games. At one point, a man with an Olympic torch, strongly reminiscent of an assassin, ran across the rooftops of Parisian buildings.
The torchbearer is apparently based on Arno Dorian, the protagonist of Assassin’s Creed Unity, the only installment in the series set in France. Ubisoft, the company developing Assassin’s Creed, is also based in France.
Judging by concept artsthe Assassin’s Creed reference was originally going to be bigger. The assassin was supposed to run across the roof of Notre Dame Cathedral; apparently, that idea was scrapped after the cathedral’s spire burned down.