Guide to Larry Niven's Ringworld

You are about to encounter the largest artifact in all Known Space, and very possibly in the universe itself. How large is that? Pretend that the Earth, as it orbits the Sun, leaves a track a million miles wide. If the sun were stationary, the result would be a ring around the sun, a ringworld with the surface area of three million Earths.Such a world exists. It was built millions of years ago by an unimaginably powerful race who then seeded it with species from all over the galaxy--and disappeared. A lot can happen in a place like that. You're going to need a Guide...