'Only man to sneak into Area 51' says what he witnessed will stay with him forever

Back in the 1990s, an anthropologist took it upon himself to undertake a seven-day trek into a highly classified United States Air Force facility located in Nevada.

Jerry Freeman travelled around 100 miles to get to the place known as 'Area 51', an air base that has long sparked whispers and conspiracy theories around the odd happenings and sightings at the site.

Many former military members have claimed to know the real purpose of the Nevada airbase, while others think they can spot alien technology in the area on Google Maps.

But back in 1996, Freeman decided to follow the trail of the 1,849 pioneers that headed west, searching for gold - nothing to do with conspiracies or alien theories.

The famous wagon train from the 19th century is well-known in American history, with the lost migrants inspiring the naming of 'Death Valley'.

Freeman travelled at night to steer clear of security patrols, and during one of the nights during his one-week expedition, he saw something shocking.

Located near Papoose Lake, a dry lake bed in Lincoln County, he told journalist and UFO researcher George Knapp that a doorway opened up in the middle of the air, letting out a blue light before closing and disappearing into thin are.

Some Ufologists have said that the country conceals a secret alien spacecraft hangar called S-4.

Recalling what he saw, the anthropologist said: "It looked like a dry lake bed to me, nothing else, but at night it was a different story.

"I could clearly see what were security lights on the perimeters and I could see lights that opened and closed near the centre of the lake."

Comparing the vibrations that night to an earthquake, he further claimed that he witnessed everything unfold for two minutes.

He did suggest that something might have been tested underground, or he was getting vibrations 'completely from Groom Lake', not being too sure - until 2013, the US government avoided mentioning Area 51 in documents, calling it 'Groom Lake' instead.

Area 51 largely remains a mystery to the public (DigitalGlobe via Getty Images via Getty Images)

"I think if they'd have caught me in there that they'd have lit me up like a Roman candle," Freeman said to Knapp in a recorded interview, before his passing in 2001.

While he was originally looking to find the lost inscriptions of the doomed group of gold prospectors that were searching for a shortcut to the 'gold fields' in the state of California, the man instead claimed to see something otherworldly.

The group were believed to have tried to cut through Death Valley to get to California, failing to make it and giving the area its name, though they had left their journals behind.

This meant that explorers could pinpoint their journey across the US.

Some of these markers were within Area 51 territory, and while he was supported by the likes of the National Park Service and the Bureau of Land Management to find these historic pieces, the US Air Force definitively told him to steer clear.

On top of all of this, S-4 become a popular talking point at the time thanks to Bob Lazar, a man that claimed to be a former government physicist who worked on what he said was reverse-engineering alien spacecraft and extraterrestrial technology.

Freeman ventured into Area 51 at night to undertake his expedition (otherhand.org)

He would claim that the government both recovered UFOs and made their own modified alien hardware in the back end of 1980s.

Lazar would even make appearances on TV, revealing that Area 51 existed and that the government would carry out classified projects there.

While the details around Area 51 are still largely unknown, it is believed that it is used to test experimental aircraft for the military.

The air base takes up an area of around 23 by 25 miles (37 by 40 km) and includes most of Groom Lake.