Factual error: In the scene where Javert commits suicide, you can see the back side of Notre Dame in the background. However the river Seine does not flow in the direction as shown in the following scenes. The river Seine flows from the east to the west in Paris, not the other way round.
Factual error: In the opening sequence, the convicts are located in a dry dock pulling on ropes supposedly connected to a listing ship in the distance. The convicts are standing in 2 to 3 feet of water which would indicate that the dock is "dry" and that the dock gates are closed. The ship will be unable to enter the dock under those circumstances. If the gates were open enough to allow the ship entry there would be 20 to 30 feet of water in the dock and the convicts would need to be up on the top of the dock to achieve their objective.
Factual error: In the scene at the inn when the man's artificial leg is pulled off, the leg's socket is a modern ischial weight bearing socket, which wasn't invented until the 1950s.
Factual error: When Javert is singing "stars" he is walking a rooftop that appears to be another church across from Notre Dame. The church of Sainte Chapelle is in that direction, but looks nothing like what is depicted in the movie. Later when Javert has his solo on the bridge behind Notre Dame, the building he was standing on earlier should be visible from that angle, but was not included in the background.