Godzilla vs. Kong's trailer may have revealed the first look at the MonsterVerse's Hollow Earth world. First introduced in Kong: Skull Island, the Hollow Earth theory posits that the Earth's core is, in fact, hollow and can be reached from the surface through large subterranean tunnels. These tunnels open to the surface at different locations on the planet, one of which is Skull Island. It's from the Hollow Earth that creatures like the Skullcrawlers emerge, but in Godzilla: King of the Monsters, it's revealed that Godzilla may have also originated from the Hollow Earth.
After being hit with the Oxygen Destroyer bomb, Godzilla travels through one of these Hollow Earth tunnels to heal at the underwater ruins of an ancient civilization that once worshiped the Titan as a god. This discovery suggests the Hollow Earth was once home to early humans as well as these gigantic creatures. Whatever is going on with the Hollow Earth, the full trailer for Godzilla vs. Kong may have shown the first real look at this world, hinting that deep within the Earth core there's more to discover than just ancient ruins.
In the Godzilla vs. Kong trailer, Kong can be seen in a jungle setting in two scenes - one where he's perched on a cliff, and another that shows him battling two new monsters, Nozuki and Warbat. There's also a scene of Kong in what looks like the mouth of a cave, placing his hand over a large hand print painted in red on the wall. All three scenes may be set within the Hollow Earth because when looked at closely, what should normally be the sky appears to actually be more land, both rocky - like in the cave - and also green and lush, as if the jungle wraps all around. This would match with common descriptions of a Hollow Earth world, where the land is concave in structure and surrounds a star at its center. This depiction is how Jules Verne describes the Earth's core in his novel Journey to the Center of the Earth, and given that story helped to popularize the theory in fiction, it's very likely the MonsterVerse would model their Hollow Earth design off of it.
Along with the trailer teasing a visit to the Hollow Earth, the Godzilla vs. Kong synopsis hints that this strange realm could be Kong's true home. Though the big ape is first discovered on Skull Island, the new movie's synopsis teases "Kong and his protectors undertake a perilous journey to find his true home" that will kick start a "mystery that lies deep within the core of the Earth." Assuming the perilous journey they embark on is a trip inside the Hollow Earth world - a real possibility seeing as the shot in the trailer of Kong at the cave mouth also shows a ship flying behind him that's likely piloted by these "protectors" - then the place from which Kong and his species originate could be the Hollow Earth. If that's the case, then Godzilla, Kong, and all the Titans may have originally come from this interior world.
The Godzilla vs. Kong trailer also mentions a war of which Godzilla and Kong are the last survivors. This war could be not only what left Godzilla and Kong as the last of their species, but eliminated most of the Titans and all the humans who once called the Hollow Earth home. This would help explain why so few Titans remain when it's suggested they were once the dominant life form but now exist only as myths. Whatever the connection, Godzilla vs. Kong appears to finally explore this strange place, descending deep within the tunnels and actually showing what is at the center of the Earth.
