When you think of a farm, you probably think about the silo, the barn, the horse stables, maybe an attractive cowboy or cowgirl hauling hay. You get the picture, right? But what you might not immediately think about are all of the little nooks and crannies where various creatures can hide out. It's these little spaces where most of the action takes place in this novel: a cinder block, a burrow under a rosebush, even an owl's nest. What is most important about setting in Rats is that the spaces provide good cover and safety for the main characters, who are pretty vulnerable because of their small size.
The novel mainly takes place on the FitzGibbon farm, in an unspecified but modern time. (There are tractors and trucks and scientists who know what DNA is, but other than that, we don't have many clues about the time period.) The main settings tell us a lot about the characters that live in them. Mrs. Frisby's house is a "slightly damaged cement block" that is furnished with "bits of leaves, grass, cloth, cotton fluff, and other soft things" (1.3). This seems like a perfect spot for Mrs. Frisby, who likes being snug and at home with her kids.
The rats' burrow, on the other hand, is huge and has "corridors that radiated […] from it in as many different directions as petals from a daisy" (11.33). They also have vaulted ceilings, glass windows, an elevator and electricity. Their burrow tells us that they are technologically advanced, but also that they steal from humans, which is something that they are ashamed of. It's the perfect set up for these rats, because it tells us right away that they're not you're average rodents. They're living in high style—but at what cost?
The flashback sections of the novel take place in the labs at NIMH and in a huge vacant mansion called the Boniface Estate. The cages at the lab are prisons, and—duh—they make the rats feel crazed and claustrophobic. When they escape and come across the Boniface Estate, it's a huge contrast to their cages. In fact, it's just huge. The bars of NIMH give way to books and a library and wide-open spaces at Boniface, both of which symbolize knowledge and freedom to the rats in the novel:
Thousands of books, about every subject you could think of. There were shelves of paperbacks; there were encyclopedias, histories, novels, philosophies and textbooks… luckily there was even one of those small ladders-on-wheels they use in some libraries to get to the top shelves. (19.27)
The rats final destination "lies deep in the forest," and the "mountains around it are forbidding, too steep and rocky even for jeeps" (22.38). The clearing that Nicodemus has in mind is a "large natural clearing, a glade where only coarse grass and wild flowers grew" (22.42). Sounds like paradise, huh?
Because the rats want to be as far away from people as possible, it's important that even jeeps can't get there. Moving to Thorn Valley may be a dream, and we don't know if the rats ever make it, but the descriptions sure make it sounds like a nice dream. Here's hoping for a happy ending.