Roadside Picnic is a 1971 Russian science fiction novel written by Arkady and Boris Strugatsky and translated to English by Antonina W. Bouis. It tells the story of the effects of the "Visitation," an event during which extraterrestrial visitors spent two days in six different spots around the earth. The title refers to a metaphor used within the story to describe the alien activity in relation to humanity; extraterrestrials briefly paused on Earth for a "roadside picnic," leaving behind their garbage and other materials much as humans might abandon their own clutter along the side of the road.
There are six "Zones" throughout the Earth, each corresponding to one of the extraterrestrial landing sites. More properly termed Visitation Zones, each Zone is the site of strange artifacts and inexplicable phenomenon, which scientists, governments, and amateur hunters explore and attempt to understand. The importance of these Zones is described in the novel's introductory interview with the character Dr. Pilman:
After all, many very important scientists have proposed that the discoveries made in the Visitation Zones are capable of changing the entire course of our history.
Zones are often explored by groups of people called "stalkers," who dangerously and illegally enter them to essentially hunt for alien artifacts. The stalkers and their activities form the basis for the plot of the novel.
Within the course of the story, the Zone specifically focused on is in Harmont, Canada. The stalker Red Schuhart makes a series of expeditions into this Zone over an eight-year period. It is full of objects that seem to defy all logic, including hazardous materials, legendary objects that can grant wishes, and others whose purposes are not known.