The Hidden Gorge is a location (probably a gorge) nearby Night Vale. It contains some sort of machines. It emits loud pulses that must be counted and interpreted in order to determine the Night Vale mayoral election results.
No one knows exactly where Hidden Gorge is, which is how it got the name "Gorge."
During the mayoral debate, candidate Marcus Vanston announced his plan to find and excavate Hidden Gorge. It is unclear whether this multi-million-dollar endeavor met with any success prior to Marcus' becoming an angel and departing from this plane of existence.
After Dana Cardinal was named the next mayor, candidates Hiram McDaniels and the Faceless Old Woman Who Secretly Lives in Your Home contested the results by shouting into the wall of a canyon they thought might be Hidden Gorge.