You might leave a cat 30 kilometers away and it might come back, but the chances are very small.
Cats have a highly developed sense of smell. Their olfactory organs, called the olfactory mucosa, have a surface area exposed to air that is three times larger than that of humans. The olfactory mucosa contains more than 200 million particularly sensitive olfactory cells, making them extremely sensitive to odors and able to detect even the faintest musky scent, one part per eight million. However, cats are not as good at finding their way around as dogs, so if you leave a cat 30 kilometers away, the chances of it returning are very small.
