Most of the obvious edges I could locate came from man made items in architecture. The sharp caulked line of a protruding corner made of a cobalt blue tiles. Geometric tile edges softened by the reflection in the polished surfaces. Ridged metal lines of an awning on bathhouse bow. The solid design soften by scroll work and stained glass.
Nature paints her edges with land, light and distance. The horizon of a sunrise in the vast flat Wyoming landscape. Layers of the Ouachita Mountains fading into fog at sunrise. A spring branch bathed in soft light as new leaves begin to unfurl.
Angles, curves and light can obfuscate or enhance the edges of man made and natural architecture.