The Hang Son Doong cave in Vietnam, located in Quang Binh Province within Phong Nha-Ke Bang National Park currently holds the title as the largest known cave in the world. With dimensions exceeding three miles (5 km) in length and 660 feet (200 m) in height, this natural wonder could house 15 Great Pyramids of Giza within its vast chambers. Its enormous passages are so spacious that a Boeing 747 could hypothetically fly through parts of the cave. The unique “skylights” in the cave’s limestone structure allow sunlight to flood in, nourishing two jungles nestled within the cave, and creating an ecosystem unlike any other on Earth.

A Discovery Decades in the Making

As per a recent report by LiveScience, Hang Son Doong, meaning “Mountain River,” was first discovered by Ho Khanh, a local resident, in 1990. Khanh stumbled upon the cave while hunting, noting the rush of wind and sound of water echoing from inside. However, surrounded by dense foliage, he was unable to relocate it until 2009. That year, Khanh successfully led a team from the British Cave Research Association, including cave expert Howard Limbert, to its entrance. Limbert, technical director at Oxalis Adventure, which now organises tours of Son Doong, described the discovery as monumental, with the team quickly recognising its scale and significance.

A Cave of Record-Breaking Dimensions

Upon detailed exploration, researchers determined that Hang Son Doong has a total volume of around 1.35 billion cubic feet (38.5 million cubic metres). This makes it the largest natural cave ever measured. In 2019, divers found an underwater tunnel connecting Son Doong to Hang Thung, adding another 57 million cubic feet (1.6 million cubic metres) to its volume. Limbert compared the discovery to “finding an additional peak on Mount Everest,” underscoring the cave’s unmatched scale in the subterranean world.

A Natural Masterpiece and Ecosystem

Beyond its size, Son Doong features remarkable geological formations. It houses one of the world’s tallest stalagmites, standing 260 feet (80 m) high, and includes the Great Wall of Vietnam, a calcite barrier that challenged explorers on their initial visits. The cave’s fossil passages offer a glimpse into the area’s ancient marine history, with fossils from sea creatures that once inhabited the region. Inside the Passchendaele Passage, named after a World War I battlefield, explorers encounter muddy terrain that mirrors the historic battlefield’s conditions.

In the heart of the cave, the collapsed ceiling forms skylights that allow light to reach its depths, nurturing thriving jungles and completing the surreal landscape of Son Doong.

In 2015, U.S. Navy pilots conducting training flights along the East Coast reported encounters with unusual, high-speed objects moving over the water. Descriptions from the pilots reveal that these oval-shaped objects appeared to rotate as they moved, covering vast distances at incredible speeds. Multiple pilots confirmed sighting these objects, which they noted were different from any known aircraft; they had no visible engines, exhaust, or defining propulsion systems.

According to Lt. Ryan Graves, a seasoned F/A-18 Super Hornet pilot with over a decade of experience, these objects were not a one-time sighting but were observed repeatedly over a period of months. The pilots’ observations, recorded on video, showed the objects not only hovering above the ocean’s surface but also appearing at altitudes of up to 30,000 feet, travelling at speeds beyond the capabilities of conventional military aircraft.

A Secret Unveiled to the Public

The public was made aware of these sightings in 2019 which was four years after they took place, when The New York Times published an article including the footage captured by the Navy. This article marked the beginning of a shift in how the U.S. government and the military approached the topic of unidentified aerial phenomena (UAP), as they are now officially termed. Shortly after, in April 2020, the U.S. Navy officially verified the authenticity of these videos, sparking renewed public and scientific interest in the nature and origin of these mysterious sightings.

Roswell and UFO Fever: A Lingering Curiosity

Public curiosity around UFOs is not new. In 1947, the Roswell Incident—where debris from an unidentified object was discovered on a ranch near Roswell, New Mexico—captured the nation’s imagination. Initial reports suggested it was a “flying saucer,” though the Army quickly retracted this, claiming the debris was from a weather balloon. This incident began a national obsession with UFOs, and the lore around Roswell has only grown over the decades. The Roswell Incident, combined with further sightings and theories around “Area 51,” left a lasting cultural impact on the public’s perception of UFOs and government secrecy.

Government Engagement and Investigation

As UAP sightings continued, the U.S. government initiated a more transparent approach to investigations. In 2021, a report was released acknowledging the existence of several unexplained UAP incidents since 2004, while maintaining that there was no evidence to suggest these sightings were of extraterrestrial origin. However, the U.S. government did highlight the need for investigation, given the potential implications for national security.

In response, the Pentagon established the All-domain Anomaly Resolution Office (AARO) in July 2022, tasked with coordinating and leading efforts to gather and analyse information on UAP. While there is no conclusive evidence linking UAP to extraterrestrial life, the objective remains to uncover the origins of these sightings, including the possibility of advanced foreign technology.

Science Takes a Stand

The rising interest in UAP has encouraged scientists to step forward in challenging long-standing stigma. NASA formed a scientific panel in 2022 dedicated to exploring UAP with an evidence-based approach. Harvard astrophysicist Avi Loeb has also made waves in the scientific community by establishing the Galileo Project, which applies observational and analytical technology to gather objective data on UAP.