Factual error: In the first scene, Dr. Dana says the asteroid heading for Earth is 5 miles wide, "larger than the one that caused the dinosaur extinction." The asteroid that did in the dinos is estimated by most scientists to have been 6-8 miles wide. (00:03:00)
Revealing mistake: Mt. Vesuvius is erupting and LaCroix's villa is collapsing around him. But while the ground "shakes," statuary falls over and the walls cave in, look closely at the fountain/pool in the center of the room. There's not a drop splashing out of it. In fact, the water's surface is smooth as glass.