The Flat Earth theory has had a lot of media coverage in recent months. Flat-Earthers fiercely believe that our lovely planet is, in fact, flat and that there's a huge multi-organisational cover-up to keep us in the dark.
However, Flat-Earthers aren't the only group who reckon our governments are keeping a huge secret about the planet. Subscribers of the Hollow Earth theory believe that...well, you can probably guess from the name.
Rodney Cluff, author of Our Living Hollow Earth and a prominent name in the Hollow Earth theory, told LADbible: "Of course the Earth isn't flat, it's a globe, but it is hollow.
"Based on my research, I would say the Earth is around 800 miles thick, from the outside to the inner surface."
The Hollow Earth theory actually goes back a really long way, with the ancient Greeks and Christians all claiming that their versions of Hell were inside Earth.
Fast forward a few thousand years and the 18th Century Astronomer Royal, Edmond Halley (of Halley's Comet fame), declared that unusual compass readings were due to the fact the planet was a hollow shell with two inner shells and then an innermost core.
Skip to the present day and, although numbers are severely dropping, there's still a staunch and determined number of believers. And who can forget the absolutely awful 2008 film,Journey to the Centre of the Earth, starring Brendan Fraser which butchered the iconic book by Jules Verne? Whatever happened to Brendan Fraser? He was everywhere for a few years and now he's vanished without a trace. Anyway, there's no time to ponder that...back to Hollow Earth.
Science tells us that the Earth is made up of unbroken layers, with liquid magma surrounding a core made of iron and nickel, but there are some who are not convinced.
Rodney says: "Explorers have actually gone down there. Some have returned and gone on to tell people what they saw, others have chosen to stay there because it's so wonderful."
Rodney also tells the story of one German man, Karl Unger, who made it into the Hollow Earth during World War II. He wrote a letter back to his pals on the outer Earth to tell them he had asked the Hollow Earth inhabitants for asylum, which was granted. You can read the full letter here.
But what's inside? Well, that's where it gets a little (more) confusing because there's some variety within the theories on what exactly is inside. However, Rodney, and many others, believe there's a whole other civilisation - complete with giant animals, eight feet tall people, rivers, a sun and a multitude of exotic plants.
Rodney describes it as 'paradise' and a 'utopia'. He thinks the people are far more advanced than us, not just in terms of technology, but they also have a deeper understanding on music and a thirst for knowledge.
They know all about us but, for the most part, don't want to interact with us (I can't blame them). However, Rodney says they do get pretty pissed off with us when we set off nukes (again, I can't blame them) as it has an impact on their lives.
He continues: "It has its own Sun, which is obviously smaller than ours, but it actually looks bigger to the inhabitants, because it's nearer. And animals, such as mammoths, still exist inside. All the animals are much bigger than what we have here, as are the people. It's also reversed - so our north is their south and vice versa.
"If anyone has the means to go, I really can't encourage them enough."
Rodney had planned to go, with a group of like-minded explorers via Voyage to Our Hollow Earth back in 2007. However, sadly Steve Currey - who was organising the trip - found out he had inoperable brain tumours just weeks before the journey was due to start and he died months later.
If you're reading this article and thinking, 'fuck, yeah, I'll go', then the openings, according to the theory, are in the North and South poles.
This picture, which is reportedly from NASA and was shared by conspiracy and UFO-lovers Secureteam 10, got Hollow-Earthers into a frenzy of excitement. Convinced yet?
So, the big question to ask Rodney: 'If this were true, why wouldn't the government just tell us?'
"Because then they would lose power," Rodney answers.
He believes the world is run by international bankers, priests and the Illuminati, who wouldn't do well out of a whole civilisation of super-smart beings found under our feet.
Rodney is hopeful that one day he will get to take part in an expedition to prove, or disprove, the theory once and for all. Until then, he's going to keep on believing.
Featured Image Credit: YouTube/SecureTeam10/WikiCommons