The Spine
From UnAnything Wiki
The Spine is a mountain range in Alagaësia that runs along or near its coast. It is weird and most people who enter it disappear. For this, or a related, reason, there is something of a superstitious taboo on it. However, Eragon could go into it a lot, even as a child, and not disappear. He found Saphira's egg there.
It is likely modeled after or inspired by the Rocky Mountains.