Summary

• The Hollow Earth concept has become a vital part of the Monsterverse, with ancient myths and 18th century theories influencing its development.
• Monarch has discovered multiple access points to the Hollow Earth over the years, but gravitational inversions and rifts make it difficult to travel there.
• The Hollow Earth is home to a diverse ecosystem, including various species of monsters, and time works differently in different realms within it. Kong is now the king of the Hollow Earth.

Over the years, the Monsterverse has provided a great understanding of the Hollow Earth world and the original Titan home of the two monsters. Originally mentioned as a theory devised by Dr. Houston Brooks to explain how Titans remain hidden in Kong: Skull Island, the Hollow Earth has evolved into the centerpiece of Godzilla and Kong's cinematic universe. And based on how integral the concept has been to each story since, it's sure to be developed further as the Monsterverse continues through projects like Godzilla x Kong: The New Empire.

The place the Godzilla vs. Kong characters went is loosely based on a real-life idea that dates back hundreds of years. Ancient civilizations had myths about an entire world that exists underground, hidden from the eyes of humans. In the 18th century, there were scientists who firmly believed in a “Hollow Earth” theory, which postulated that the planet was actually hollow, and that there’s a massive, empty space under the surface. The scientific community disproved the concept long ago, but the Monsterverse brought it back in an interesting way and made it a vital part of three movies, plus Apple TV+'s Monarch spinoff series.

Hollow Earth History & Timeline In The Monsterverse

The first mention of the Hollow Earth in the Monsterverse was dropped in Kong: Skull Island, set in 1973. At the time, the concept of a Hollow Earth was supported by Dr. Houston Brooks (Corey Hawkins) and Bill Randa (John Goodman), who believed that one of the entry points to this place was at Kong’s home, Skull Island. Monarch: Legacy of Monsters' flashbacks revisited the origins of the theory, and revealed that the notion of an underground Titan world occurred to Randa first. Randa stumbled upon the idea of a Hollow Earth in 1956 and shared it with the government. The events of Monarch: Legacy of Monsters confirmed that his wife, Keiko Randa, fell into a Hollow Earth entry point in 1959.

In 1962, the Department of Defense set up Operation Hourglass, a project designed to allow humans to enter a tunnel they believed connected to the Hollow Earth world. When the expedition cost people their lives, the government ended their Monarch funding, which explains why it took so long for people to make any headway in regards to the Hollow Earth. It was established in Monarch: Legacy of Monsters that over the years, Monarch had become aware of multiple Hollow Earth access points. In fact, three humans (May, Cate Randa, and Kurt Russell's Lee Shaw) landed in the Hollow Earth world in 2015, where they found a still-living Keiko.

Until the release of Monarch's show, of course, it was understood that Monarch didn't prove the Hollow Earth's existence until 2019. Five years after Godzilla's battle with the MUTOs, Monarch discovered an underwater Hollow Earth tunnel, as depicted in Godzilla: King of the Monsters. After Godzilla was hit by the Oxygen Destroyer, Monarch descended into the ocean to revive him. In doing so, they found a secret cavern where the Titan was recuperating and an abandoned city where they worshipped Godzilla and the other Titans. The hidden Hollow Earth world was officially discovered by Monarch another five years later in Godzilla vs. Kong's ending.

The Hollow Earth World & Energy Source Explained In Monsterverse

Much more about the Hollow Earth was uncovered in Godzilla vs. Kong. The story confirmed it to be the “birthplace” of the Titans, which means that many of them must have left their original home for some reason or another. Plus, it was explained that this place isn’t just a lifeless, empty cavern. Just as Walter Simmons said, the Hollow Earth possesses an “ecosystem vast as any ocean.” It has green grass, forests all sorts of different monsters, water, trees, mountains, clouds, and more. And according to Lee Shaw, the Hollow Earth consists of various "realms," which accounts for why the place seen in Monarch: Legacy of Monsters is visually different from what was shown in Godzilla vs. Kong.

As for how such a place could exist at all, Simmons made sense of it when he told Dr. Lind about a mysterious “lifeforce” that somehow sustains the Hollow Earth’s world and keeps it going, much like the sun sustains the Earth’s ecosystem. This lifeforce relates to the ring of blue energy Kong found. It was activated when he placed the axe of his ancestors in a crevice that acted as a keyhole of sorts. Whatever it was, it was connected to Godzilla, who is presumably powered by the same atomic energy. Godzilla’s link to it was confirmed when he responded at the exact moment that Kong triggered it.

Why Traveling To The Hollow Earth Is So Difficult

As noted above, Monarch has knowledge of multiple places where Titans can travel to and from the surface and the Hollow Earth. Access points have been found on Skull Island, as well as in Alaska, Antarctica, Kansas, and Kazakhstan. However, knowing these locations hasn't made getting to the Hollow Earth world an easy task for Monarch. The Hollow Earth entrances have what Dr. Lind described as a “gravitational inversion”, which is why APEX’s aerial vehicles were a necessary form of transportation.

Monarch: Legacy of Monsters clarified this further, establishing that "rifts" block the way between the surface and the Hollow Earth. They act as portals. Before the development of APEX's vehicles, the only way through for humans was to piggyback on a Titan. General Puckett mentioned in the show that when a Titan passes through, it "stabilizes" the rift long enough for it to become "passable" for humankind.

Hollow Earth's Ancient Titan War

While they were in the Hollow Earth, Dr. Andrews said that there were myths about an ancient “Titan War” that involved the ancestors of Godzilla and Kong. It would seem that long ago, both of their species lived down there and fought each other. This does make sense, as it finally clears up the Godzilla Easter egg in Kong: Skull Island’s post-credits scene. A cave painting showed the two fighting, which did indicate that Godzilla and Kong’s ancestors shared a history. It reappeared again in Godzilla: King of the Monsters.

It would seem that this war is the reason why the Kongs no longer live in the Hollow Earth. The fact that the Kongs lived on Skull Island despite once ruling a much more expansive region suggests that they were driven out. It may be that losing the Titan War to Godzilla is why they were forced to relocate. Whether or not that's really the case may be confirmed or debunked by Godzilla x Kong: The New Empire.

Creatures Confirmed To Live In The Hollow Earth

Due to the sheer size and scope of the Hollow Earth world, there's no doubt that hundreds - if not thousands - of different species of animals and monsters occupy this place. Thanks to Godzilla vs. Kong and Monarch: Legacy of Monsters, a handful of its residents have been shown off. One, the Leafwings, also dwell on Skull Island. So far, the rest are unique to the Hollow Earth and have yet to develop a known presence on the surface. Among these species are the Bramble Boar from Monarch: Legacy of Monsters, the Rock Critter, the Hell Hawk, the Warbat, and Titanus Doug.

How Time Works In The Hollow Earth

For at least one of the Hollow Earth realms, time works differently in the Hollow Earth. This was evidenced by two of the biggest twists in Monarch: Legacy of Monsters. As a result of what went wrong with Operation Hourglass, Lee Shaw was lost in the Hollow Earth for a week (from his perspective), but when he returned to the surface, 20 years had passed. This served as the explanation for why Shaw looks so much younger than his true age.

An even more surprising example of the Hollow Earth's time rules presented itself when it was revealed that Keiko Randa still appears to be a woman in her 30s despite being stranded in the Hollow Earth between 1959 and 2015. But for her, she was only there for 57 days. She chalked up the strange passing of time to the "gravitational distortion" of the Hollow Earth causing some sort of "warping of space-time." For now, it remains to be seen if time works in the same way in other Hollow Earth realms.

Kong Is The New King Of The Hollow Earth

The ending of Godzilla vs. Kong offered a new twist to Kong’s Monsterverse story. Kong being sucked into APEX’s mission to build Mechagodzilla handed him numerous challenges, but in the end, it gave him a brand-new role. Godzilla may be the alpha of the surface world, but Kong is the “king” of the Hollow Earth now. It’s a fitting way for his Godzilla vs. Kong arc to end, given the fact that Hollow Earth – and not Skull Island – is the real home of his species. Chances are, though, Kong's reign won't be without complications. Godzilla x Kong: The New Empire's Skar King is likely to offer a huge challenge to Kong's newfound authority.