The setting of Mary Shelley's Frankenstein is most directly stated in the opening of the introduction to setting provided by eNotes.
The setting of the novel ranges all over Europe, emphasizing places with which Shelley herself was familiar: Italy, Switzerland, Germany, France, England, Scotland, Ireland, and even the Arctic. The tale begins and ends in the Arctic with the explorer Robert Walton seeking a northwest passage.
Given that the locations of the novel span "all over Europe," the settings are both man-made and naturalistic.
Much importance lies in the fact that the setting of the novel bounces back and forth between settings created by man and settings created by nature. In fact, this movement mirrors the theme of Science verses Nature.
Much of the novel speaks to the fact that by creating a being, not birthed by a woman, Victor has thrown the balance of nature askew. The movement from his lab, to his home, to the mountains, to a jail cell speak to the theme of the novel with the same fluidity that the novel forces readers to question the world of science and the world of nature.
Some may find it curious that Victor is only at home when surrounded by nature.
When happy, inanimate nature had the power of bestowing on me the most delightful sensations. A serene sky and verdant fields filled me with ecstasy. The present season was indeed divine; the flowers of spring bloomed in the hedges, while those of summer were already in bud.
When in his laboratory, on the other hand, Victor alienates his friends and family, even ignoring his own health.
This proves the importance of the flow of the setting moving back and forth between the world of the natural and the world of science.