 At one point in ancient history, pre-catechism, people began carving out large cities underground. What's that all about? Wait till you hear this. For centuries, people have told tales of caves and tunnels deep inside the earth. Subterranean passageways that led to lands of gods and monsters and treasures from beyond the stars. Shouldn't we be looking for proof of their existence not in the heavens above, but in mysterious worlds deep beneath the surface. In 1963, a simple home renovation in the town of Darren Cuyoo led to an extraordinary discovery when a cave wall was opened revealing a passageway to an underground city tens of thousands of years old and more than 280 feet deep. It is mind blowing and is just one example of hidden knowledge of a civilization that could not live on the ground level of the earth. There are 15,000 ventilation shafts going down to the deepest levels of the ancient city. Incredibly, there was even evidence of religious centers, storerooms, wine presses and stables for livestock. It would have been a massive undertaking for any civilization even in modern times with modern equipment. But in those days, it would have been unimaginable. You could easily put it on a par with the undertaking equal to the pyramids at Giza. It is mind boggling to understand how they could have done this. Perhaps they had help from some other civilization. But just who built this massive underground city? And what mysterious force drove them to live underground? Why would people want to live deep underground in these caverns? It is as if they knew something, something was coming, something massive indeed, a cataclysm. Perhaps the builders of the pyramids were the same race of beings that built these underground cities all around the globe. Perhaps they convinced humans across the world that they could avert the cataclysm if they waited it out underground. Perhaps some civilizations still exist deep within the Earth today. Remember, we told you NASA received distress signals from within the Earth at no less than six locations worldwide since the early 1990s. In the 1920s, Captain Bird made world headlines by flying over the North Pole and becoming the first man to fly solo over the South Pole. Many are to believe that the famous explorer went even further and that on February 19th, 1947, Admiral Bird piloted a plane through a hole near the North Pole into the interior of the Earth. A flying saucer type craft took control of his airplane with some kind of tractor beam and they landed him near an inner Earth city. And the message that they had for us was that they considered themselves the guardians of this planet. We had just blown up a couple of cities in Japan a couple of years before, so this was the message that he was given, a warning. But when Bird got to Washington, they put a lid of secrecy on this, that this was not to go public at any cost. Some say Admiral Bird's own account of this flight into the Hollow Earth is detailed in his secret diary published in the 1990s, almost four decades after his death. The rumor was he found a world of flying machines and people and more advanced machinery than that of the surface people. Could there really be vast open spaces within the Earth where advanced civilizations live? Could civilizations really have come to Earth centuries ago and hidden the evidence of their journeys deep within caves and tunnels? Perhaps we have only just scratched the surface of our planet's underground mysteries. If so, what clues to our distant past might still be waiting to be found and hiding in the darkness? What do you guys think of this anyway? Comments below? Thanks for watching. Admiral Bird, you've been to both the North Pole and the South Pole. Is there any unexplored land left on this Earth that might appeal to adventurous young Americans? Yes, there is. And not up around the North Pole because it's getting crowded up there now because they find out it's really usable, not only to live in, but militarily. But strangely enough, as left in the world today, an area as big as the United States that's never been seen by a human being. And that's beyond the pole on the other side of the South Pole from Middle America. And I think it's quite astonishing that there should be an area as big as that unexplored. I tell you one reason they're interested. It's by far the most valuable, important place left in the world for science. That's why the scientific groups all over the nation are really interested. But more important than that, it has to do with the future of the nation, those to come after us, or even during your lifetime.