Answer: places of equal altitudes
Notes: In cartography, a contour line (often just called a “contour”) joins points of equal elevation (height) above a given level, such as mean sea level. Contour lines are curved or straight lines on a map describing the intersection of a real or hypothetical surface with one or more horizontal planes. The configuration of these contours allows map readers to infer relative gradient of a parameter and estimate that parameter at specific places.
