MEGA STRUCTURE

A megastructure is an artificial construct of enormous size. The term is informal but generally megastructures are at least a few thousand kilometers in size along one dimension. Megastructures appear most frequently in science fiction, though arguably the Great Wall of China is a megastructure. The Great Wall can be seen from low earth orbit, but so can highways, fields of crops, and large buildings. Low earth orbit is only 200 km (125 mi.) up so this makes sense. Megastructures are most frequently seen in science fiction, and it seems like only a matter of time until our civilization starts to build them. A megastructure is meant to be a contiguous, self-supported entity - that is, not composed of an aggregate of smaller constructs.