shavedape
Well Known GateFan
An AU is the distance from the Earth to the Sun roughly speaking.
The Ringworld has a complete ecology and a fully functioning biosphere - the book describes it in some detail (it even has systems that handle erosion that are self powered and automated).
Don't want to get into spoilers but...the synopsis said there was a tech break down and the inhabitants had reverted to more primitive behavior. So I assume if the system wasn't operating then things would be messed up with the ecology/environment. Plus, the circumference was 600 million miles "long". Did they somehow transport that much soil and geological material in the creation of this device, and if so where did they get all of that material from to begin with?
I'll see if I can find the book because it's a very interesting concept. Even fictionally based the story begs many questions.