One reason Sylvester Stallone agreed to act in this movie was to help him overcome his fear of confined spaces. He'd agreed to appear in Cliffhanger (1993) to help him overcome his fear of heights.
Rob Cohen originally wanted Nicolas Cage to play Kit Latura. Universal execs felt he was more of a "character actor", and Sylvester Stallone was more commercially viable.
Sylvester Stallone said this would be his last action film because he was getting too old for the genre. However, he made Driven (2001), Rocky Balboa (2006), Rambo (2008), and the Expendables movies afterward.
Sylvester Stallone was paid $17.5 million to appear in this film.
The tunnel sequences were filmed in Rome's Cinecitta Studios, on a set a third of a mile long. Cinecitta was chosen as the main studio set because of its enormous floodable sound stages.