The giant storage domes that pop on the sides of highways are harder to miss. According to Canada Salt Group Ltd., the structures are used to store massive amounts of road salt for snowstorms. Road salt doesn't go bad as long as it's kept dry, so it's cost-effective to store the material in bulk on the side of the highway. The reason road salt is stored in domes instead of more conventional four-walled buildings is to maximize the clear space inside. So until roads with built-in salt become a thing, storage domes will likely remain a fixture of our roadways.