Since The Man in the Iron Mask is a work of historical fiction, its historical setting obviously plays a large role. Dumas draws on the historical setting of King Louis XIV's court to build a believable version of events. He is literally re-writing history, and uses details from the era to help him in that task.
Since the story is mostly driven by plot and dialogue, spatial settings in The Man in the Iron Mask usually do not matter so much – the characters usually hang out in some type of room, whether it be a prison cell, bedchamber, or audience hall. Dumas does have a tendency to stage some beautiful settings for his characters, however, and when he pays attention to the setting of a scene, he really pays attention to it. The theatrical quality of the scenes tends to reflect Dumas's previous career as a dramatist. The black horse chasing a white horse across plowed fields on a moonlit night, for example, or the destruction of the Locmaria grotto, are spectacular. His quieter scenes are given no less attention. The scene between Aramis and Philippe in the forest as the prince decides upon his destiny, or Athos and Raoul's gravesites at the little chapel in Blois, are rendered in loving, poignant detail.
But let's return to this idea of Dumas as writing an action movie. When the creators of Crouching Tiger, Hidden Dragon wrote the final fight scene, they staged it in a bamboo forest. In The Matrix, one of the best hand-to-hand combat scenes takes place on an empty subway platform. Our point is, no matter how great an action sequence is, it looks even better when it has a spectacular backdrop. And that Dumas delivers in spades.