Acre NOT Jerusalem, among other mistakes
In May of 1291, it was Acre that fell, ending the Crusader Kingdom of Jerusalem, not the city of Jerusalem as this movie confuses.
Among other things that Victor Garber says that Templar found the body of Christ, which doesn't go with the Catholic belief that Christ left no bodily remains. Hence, why the important relics of Christ are not finger bones or a skull, but instead the tears, fragments of the shroud and the cross.
These are just two of the many mistakes in this movie, I hope the book is a bit closer, with how popular it seems to be.