Author's Note: Ringworld is an enormous artificial world built in the shape of a ring, with gravity generated by the ring's spin. Hundred mile high walls rim the edges to keep the atmosphere in. Although the walls are tall, they shrink to insignificance in comparison to the surface area of the world.
An inner ring of rectangular panels connected by impossibly-strong wire provide the shadows necessary for “night” and “day.”
Ringworld has a surface area 3 million times that of earth. In the novel, four adventurers crash-land on Ringworld and see a small percentage of its vast landscape and native inhabitants.