Megastructures are artificial constructs so huge that they challenge our preconceptions of size.
A megastructure, by definition, has to be a single, unified structure. A modern city may be huge in scale, but its is actually composed of many thousands of individual buildings, all built at different times for different purposes. The Great Wall of China may be considered a megastructure, however, as it is a single complete structure with one dedicated purpose.
Megastructures may be intelligent life's ultimate expression of existence, as they challenge the very scale of the universe.
Planet Scale Megastructures are constructs built on the size of solid celestial objects, such as asteroids, moons, and planets.
Miniature world in the Great Dark.
Large colonies on minor bodies.
Artificial planetary rings.
Multiple celestial objects in the same orbit
Moon- and planet-sized stations.
Planet-sized hollow spheres.