Continuity mistake: When Roy plunges into the water, there should be pieces of rope around the bottom of the pulley device he is hanging from, but there is none.
Continuity mistake: In the beginning, Lin Wang goes from holding the puzzle box in one shot to holding her father's hand in another shot.
Continuity mistake: In the final fight, we see Rathbone flip his sword at one point so he is holding it "properly", but in the previous cut he was already holding it in the right way. This is because much of the fight was cut in editing, and several pieces of sword fighting were taken out.
Continuity mistake: When Owen Wilson is climbing the minute-hand of Big-Ben, his legs change position between a few shots.
Continuity mistake: If you look closely during the fight scene in the library, the guy that Jackie Chan traps in the ladder is not the same person from the moment he gets trapped to the moment he gets knocked out. (00:50:45)
Deliberate mistake: When Roy plunges into the water, it is pretty obvious he is a dummy.
Factual error: Near the start, we see a long shot of New York Harbor, where we can see the Statue of Liberty under construction. When we see the statue it's green, which comes from the statue corroding, which it hasn't had time to do.
Continuity mistake: When John is trying to lift Roy out of the water it seems to take a full rotation of the turnstile to raise him up a foot above the water, but when John is fighting with the guard he moves the turnstile back and forth about 2-3 feet each way and you see Roy dipping in the water and raising out about a foot above the water then back in and out of the water.
Factual error: Chon Wang and Roy O'Bannon crash their car into Stonehenge. In the shot where you see them walking away from Stonehenge, the landmark is shown on a hill. In reality, Stonehenge is on a flat plain.
Continuity mistake: During the climatic fight scene between Jackie and the baddie in the Clock Tower, the background was the inner side of the clock. There was silhouette of the clock's hand without Owen on it when Jackie was dueling the villain on the platform. However, when Jackie and the villain crashed through the same clock face, Owen was hanging on the clock's hand. (01:33:30)
Factual error: The red coated British Guards are always shown armed with No. 4 Lee-Enfield rifles. The film is set in 1887 - the No. 4 rifle did not come into use until WW2.
Factual error: When Chan and Wilson hitchhike, they stick out their thumbs to catch a ride from a buggy. Hitchhiking in this way wasn't popular until the 1930's; the movie is set in the 1880's.
Revealing mistake: It is really obvious Jackie Chan was on a wire when holding onto Roy at the end. His body floats and moves in a very unnatural way.
Revealing mistake: When Roy and Chon arrives in London you can see ships on the river Thames. However the sails on the ship are to tall for the ships to be able to get under the bridges. (00:21:45)
Continuity mistake: At the end of the library fight scene, a guard is trapped in a rung on a ladder, leant backwards against the bookcase (so the guard is "on his back", head facing the books). Between shots, the amount of his body trapped in the rung changes, going from his shoulders, to most of his arms. It keeps changing between shots.
Continuity mistake: In the fight scene in the library, Chon throws a small book at the guard. When the guard cuts it using his sword, the pages that were/are in it are big and white.
Factual error: In the scene where Owen Wilson and Jackie Chan confront the street urchin who stole Wilson's watch, Wilson tells him they have "parents who love us", but as he says it he is looking over way over the boy's head. [If you watch the outtakes, Owen Wilson says he feels "so mean" talking to a child that way, so it's possible he simply couldn't be that mean to a child while looking him in the eye. Or he could have been trying to keep from laughing. Either way, it's still a valid mistake, this is just a possible explanation.]
Revealing mistake: When Owen catches Jackie at the end, you can see Jackie Chan hitting the "glass" of Big-Ben, which bends like a painting or other set prop. This happens very quickly.
Continuity mistake: Towards the middle of the movie Wilson is sitting down with some wine beside him on the table talking to Chan. In the first shot the glass is almost full, in the next shot it is nearly empty and has moved, and in the next shot it is once again almost full.
Factual error: During the scene when they are about to try to drown Jackie & Owen you can see the ceiling. On it are large shop lights. Even though lights were invented over 50 years beforehand, lights that new looking and of that kind were not.
Answer: It is never really mentioned, but we can assume it is the home of some noble or "higher class" person, from all of the elaborate things.