Underground city (A Frightened Hound Meets Demons Underground)

The Underground city is under Seattle.

Season one
The gang investigates the weird happenings of some ancient demons. They learn that the demons are after a talisman that will drive them back into the iron lid of an underground city where they belong. (A Frightened Hound Meets Demons Underground)

Appearances

 * The Scooby-Doo Show
 * 110. A Frightened Hound Meets Demons Underground