Digital and Film
This combo is either the best of both possible worlds…or the worst.
In Gladiator's first scene—the huge battle scene where the Romans totally annihilate the Germanic barbarians—looks as real as can be. And it should—it was filmed in merry old England.
But that realness is complimented by some super-impressive (especially by circa-2000 standards) digital effects.
Digital was used when necessary either to recreate what is long gone or to enhance things—the size of the Colosseum, for example. (Scott famously remarked that the real Colosseum wasn't big enough for his purposes). They also made very good use of some green screen tigers.
But Gladiator does, in many instances, showcase the way that film and digital effects can work harmoniously. While the first two rows of the made-for-Gladiator replica of the Colosseum were filled with actual people (extras, mostly), while the remaining stands were filled with cardboard cutouts. During post-production, the savvy digital dudes over at The Mill added additional tiers to the shots, along with lots of other fancy effects.
The character of Proximo's another example of the way in which the film blends both film and digital. The late, great Oliver Reed, who plays Proximo, died during the making of the film.
But death is only a minor hiccup when it comes to movie magic. The guys over The Mill used shots of a stunt double in the shadows, and then overlaid a digital version of Reed's face.
Total amount of face-time added: two minutes. Cost: 3.2 million dollars. (Source)
But hey, when your budget's somewhere around 100 million, you can afford to spend that much to get the best.
And get the best the producers did. Juba's wonderment upon seeing the Colosseum for the first time—"I didn't know man could build such things"—is our own upon viewing Gladiator and its stunning mixture of two filmic modes: we didn't know man could make Oliver Reed and ancient Rome come back to life.