Megastructures Ringworld 2

Part of the "Megastructures: The Visual Encyclopedia" book project, on sale now at http://www.neilblevins.com/megastructures/megastructures.htm

A Ringworld is an artificial ring in space large enough to maintain an atmosphere and habitable land. The ring spins to create g-forces, and inner walls could be used to hold in the atmosphere. “Stellar Scale” rings could have a radius roughly equal to the radius of the Earth's orbit around the sun, and could in fact have a sun at its centroid.