Topographic maps are distinguished by the contour lines that portray the shape and elevation of the land. They display the three-dimensional ups and downs of the terrain on a two-dimensional surface. Topographic maps usually portray natural features, such as mountains, valleys, plains, lakes, rivers, and vegetation, and man-made features, such as roads, boundaries, transmission towers, and even major buildings. Topographic maps are used by professionals for engineering, environment management, conservation of natural resources, energy exploration, public works design, and general commercial and residential planning. They are also used by individuals for outdoor recreational activities such as camping, hiking, biking, and fishing.