At 277 miles (445 kilometers) long, up to 18 miles (28 kilometers) wide, and 1 mile (1.6 kilometers) deep, the Grand Canyon is one of the most beautiful and awe-inspiring places in the United States.

The Hopi Indians believe it is the gateway to the afterlife. Its sheer immensity and mystery attracted more than 6 million visitors in 2016.

But what those people probably don’t know is that the Grand Canyon might once have been the home of an entire underground civilization.

But where are they now? And why did they abandon the canyon? Hosts Matt Frederick, Ben Bowlin, and Noel Brown jump straight into the folklore, the legends, and of course, the conspiracies to find out what really happened to the Grand Canyon’s Lost Civilization in this episode of Stuff They Don’t Want You To Know.

And no one has been able to find these supposedly massive caves since. Was this some elaborate hoax, may be perpetrated by the Gazette to sell papers?

That’s certainly a possibility, but it doesn’t fly for many conspiracy theorists. Some argue that the Smithsonian Institution has purposely wiped Kincaid and Jordan from their records and actively destroyed artifacts that don’t agree with the “status quo story” of human history.

Others think the caves hold a passage to the fourth dimension, where the reptilians (yep!) who have secretly run the world for thousands of years emerge into our world. Still, others believe the area is top-secret and closely guarded, like Area 51.

So is this series of caverns proof of a long-lost, possibly Egyptian civilization that’s simply being covered up by the Smithsonian, or is it a passageway into this dimension for our reptilian overlords? One thing is for sure.