Factual error: When M tells Allan Quatermain that he and his team have four days to go from London to Venice, he answers that this is impossible, and captain Nemo replies that it will be possible thanks to his science-fictional devices. Actually, on late 19th century railways, this trip would have taken less than two days. For example, the Peninsular Express departed every Friday afternoon from London, and it arrived at Brindisi, a considerably more distant town in southern Italy, on Sunday afternoon. (00:16:39)
Other mistake: When Quatermain impales the henchman at the beginning of the film, the rhino is hung high on the wall and the tip is much higher than the spot the man hits, Quatermain would have to have lifted the man higher than he does to achieve this.
Continuity mistake: From the meeting with M to Dorian Grey's place, the amount of makeup showing Skinner's head varies too quickly to be real.
Factual error: In Kenya, Alan Quatermain pushes a guy back with a table and impales him on a horn on the wall. The table hides the wound, but the horn punches through. If this guy was impaled on that horn, it would have some blood on it. However, it's just as totally clean as it was before.
Answer: After Quartermain is buried, we see a witch doctor performing magic above his grave and the clouds darken indicating something is about to take place. The witch doctor is chanting "Return" and the grave begins to shake. Although we do not see Quartermain come back to life it is most definitely hinted that he did and left room for a sequel which never came to pass.