Factual error: The scenery is set in Berlin, following the 1989 Re-Union of Germany. Only thing is: the guards at the archive building use AK-47s, while after the Re-Union, the East German National People's Army and the West German Bundeswehr (Federal Defense Force) were joined - and the West Germans don't use any AKs.
Factual error: CDR Crighton has on his astronaut flight suit. He is wearing an American flag on his right upper arm. But the flag has the field of stars to his rear. It is a flag designed to be worn on the left arm, not the right.
Factual error: The group finds an underground sea and there is a flock of pterosaurs flying overhead. The professor identifies the pterosaurs as the missing link between pterodactyls and archaeopteryx. This is not true as archaeopteryx (and other birds) did not descend from pterosaurs but from a branch of theropod dinosaurs.