The main location in *Night of 100 Frights* is Spooky Island, where the gang investigates a series of strange occurrences. The island itself is the main setting, with no hidden lab or similar area.
However, there are a few locations on the island that could be considered "secret" due to their unusual features, including:
* The abandoned lighthouse: This structure is seemingly haunted and plays a pivotal role in the film's story.
* The old cemetery: The cemetery is shrouded in mystery and becomes a focus of investigation.
* The secret tunnels under the lighthouse: These tunnels connect the lighthouse to a mysterious underground network.
If you're thinking of a different Scooby-Doo movie or episode, please provide more context, and I can try to help you find the "secret lab" you're looking for!