The Rusty Ruins are actually rusty ruins. They're the ruins of a city built by a previous civilization, called the Rusties.
(Possibly us, because lots of them died in their cars when some disaster struck. We'll hear more about this disaster soon, so don't get scared of cars. We promise you that they are not Transformers.)
The Rusties lived a very different lifestyle without hover technology. (They put all scientists into researching teeth-whitening and hair-growing technology.)
Every ugly goes to the Rusty Ruins on a school trip, but Shay and Tally explore much more of the city. They even ride their hoverboards on a roller coaster, even though the roller coaster isn't totally intact.
Tally gets angry at Shay for not telling her about the gap she needed to jump, but gets over it quickly. Because dangerous roller coasters are the foundation of most friendships.
Shay tells Tally that she knows this stuff about the Rusties because she has a friend who told her. And this mysterious friend, he lives out here in the wilderness, says Shay—and they're going to meet him.