Were the Nazis building a flying saucer? Experts hint mysterious 'Flytrap' construction - dubbed 'Hitler's Stonehenge' - that was built over top secret tunnels was launch pad for experimental disc aircraft

A mysterious 'Flytrap' structure built above a top secret network of tunnels by the Nazis in the Second World War might have been a launch pad for an experimental 'flying saucer', experts have suggested.

The bizarre arched, circular concrete structure was part of the clandestine Project Riese operation, in which a deep network of tunnels were built by concentration camp prisoners in 1944 in the Sowie Mountains in Nazi-occupied Poland.

The purpose of the tunnels themselves remains shrouded in mystery because fleeing Nazi forces destroyed documents and materials before Soviet troops occupied the area after their defeat in the war.

Now, a new UKTV Yesterday documentary consults a series of historians and archaeologists who give their views on what the tunnels and weird surface structure - which is also known as 'Hitler's Stonehenge' - were used for.

In tonight's episode of Secret Nazi Bases, Forensic archaeologist Robert Sparling said the Nazis may have been 'playing' with technology that would 'look like a flying saucer' and had 'glowing propulsion systems'.

He said he would not be 'surprised' if the Flytrap was connected to such a device and suggested the structure was a good shape to support it and allow it to lift off.

Other theories delved into in the programme are that the Flytrap and tunnels were used as part of the Nazis' pioneering helicopter programme; that Project Riese was the home of a nuclear weapon project; or even that some kind of 'anti-gravity' device was being developed there.

Polish project manager Krzysztof Szpakowski, who has carried out work in the tunnels claims in tonight's show that his and an employee's phone rang while they were working deep in the tunnels, where it should be 'impossible'.

He said he is 'convinced' that 'electrical impulses' caused by old Nazi futuristic technologies that remain hidden in the tunnels caused the phones to ring.

A mysterious 'Flytrap' structure built above a network of tunnels by the Nazis in the Second World War might have been a launch pad for an experimental 'flying saucer', experts have suggested. The bizarre circular concrete structure is discussed in tonight's episode of Secret Nazi Bases, on UKTV channel Yesterday. It  was part of the clandestine Project Riese operation, which saw a deep network of tunnels built by concentration camp prisoners in 1944 in the Sowie Mountains in Nazi-occupied Poland.  Above: The Flytrap structure, along with how the Nazi flying saucer might have looked on top

Work began on the tunnels (shown above in tonight's programme) in 1943 as Nazi dictator Adolf Hitler sought a way to regain the upper hand in the war against the Allies. They were built deep into the igneous rock of the Owl Mountains in Lower Silesia

More than 5,000 of 13,000 slave labourers - including children as young as 10 - were worked to death constructing the tunnels in Lower Silesia, with many of them surviving little more than a few months as the Nazi officers forced them to work them 24 hours a day, seven days a week.

Work began in 1943 as Nazi dictator Adolf Hitler sought a way to regain the upper hand in the war against the Allies.

The situation for Germany had become progressively worse since the decision to invade the Soviet Union in 1941.

The tunnels, which were hand-carved out of hard igneous rock, were the perfect place for the Nazis to work on projects because they protected against the threat of the increasingly effective Allied bombing campaigns, which had decimated the above-ground war effort.

Because of the need to keep the tunnels a secret from the Allies, many senior Nazi officials were not aware of the existence of Project Riese.

The tallest parts of the tunnels are 36ft high, making them a plausible location for large weapons or machines to be constructed.

Forensic archaeologist Robert Sparling said the Nazis may have been 'playing' with technology that would 'look like a flying saucer' and had 'glowing propulsion systems'. Above: A mock-up of the flying saucer, which is shown in tonight's programme

The tunnels, which were hand-carved out of hard igneous rock, were the perfect place for the Nazis to work on projects because they protected against the threat of the increasingly effective Allied bombing campaigns, which had decimated the above-ground war effort. Above: A surface building seen at the site in a 2015 photo

More than 5,000 of 13,000 slave labourers - including children as young as 10 - were worked to death constructing the tunnels, with many of them surviving little more than a few months as the Nazi officers forced them to work them 24 hours a day, seven days a week. Above: Images of the tunnels which were taken in 2015

Polish project manager Krzysztof Szpakowski , who has carried out work in the tunnels claims in tonight's show that his and an employee's phone rang while they were working deep in the tunnels, where it should be 'impossible'

The tunnels were heavily guarded with MG machine guns in place at their entrance. Because of the need to keep the tunnels a secret from the Allies, many senior Nazi officials were not aware of the existence of Project Riese

The tunnels, which were hand-carved out of hard igneous rock, were the perfect place for the Nazis to work on projects because they protected against the threat of the increasingly effective Allied bombing campaigns, which had decimated the above-ground war effort='

World War Two expert Patrick Ney said: 'There was something that they the were doing that was very very important. 

'You only have to look at how much concrete was involved to know that this was one of the most important engineering projects that the Nazis were doing.'

Fellow historian Rob Bell added: 'For them to put this amount of effort, these kinds of resources into a secret project here, there must have been something incredibly important to their war effort going on.'

Dr Deborah Neill said: 'It stands to reason that some of these tunnels could have been designed as places where they could continue to manufacture even whole airplanes potentially. The sheer scale and size of the tunnels.'

The Nazis are known to have moved some operations - such as the V2 rocket programme – underground after production facilities were destroyed by bombs.

The Flytrap – which was built above the tunnels and is around 60feet across and 30feet tall, would have been a 'big undertaking' to construct, architect Brooke Guzar said.

Historian Professor Robert Watson, who is the author of more than 40 books, said it is 'infuriating' that experts still do not know what why the Flyrtrap was built.

Forensic Engineer Mr Sparling said it may have been associated with a 'flying saucer' machine.

A far more plausible theory is that the tunnels and maybe the Flytrap itself were used to test the first helicopters. Nazi scientists were among the first in the world to develop prototypes of the flying machines. Above: How the helicopter might have looked while inside the tunnel

Scientist Friedrich von Doblhoff began working on the technology in the 1930s and, by 1941, had a working prototype. Above: The Doblhoff/WNF 342 in action

Another even more bizarre rumoured project covered in the programme is that of Die Glocke – 'The Bell' in English

Above the tunnel is a host of abandoned equipment, including an old car, a truck and old rail trolleys

'Air supremacy was going to be part of what determined the outcome of the war,' he said.

'So maybe they were playing with some type of technology that would look like a flying saucer that had glowing propulsion systems.

'I wouldn't be entirely surprised at all if this fly tap were associated with the development of that kind of device.'

He added: 'Where you wanted it to lift off the ground you would need some kind of structure to initially support it, allow the air to flow out from underneath it, underneath the pillars.'

A CGI graphic showing the alleged flying saucer depicts how it might rested on top of the Flytrap.

Dr Neill added that the rumoured disc-shaped object might instead have been used to create energy.

She said: 'One speculation that an object they were working on that could have generated energy looked a little bit what like science fiction writers would have described as a flying saucer but that was in fact not at all what its purpose was.

'They were using all kinds of different devices and structures to try to work out how they could generate energy.'

Another even more bizarre rumoured project covered in the programme is that of Die Glocke – 'The Bell' in English.

It was first described by Polish journalist and author Igor Witoski in a 2000 book.

Mr Bell explained: 'Die Glocke, or the Nazi Bell, is this rumour that has lingered for decades about this Nazi bell-shaped object that is associated with anti-gravity, or free energy or some kind of pseudo-scientific concept.'

Professor Watson added that it was said to be a 'large bell-shaped device that could rotate' and perhaps create a state of anti-gravity – the hypothetical phenomenon of a place or object which is free from the force of gravity.

Tonight's programme posits the outlandish suggestion that the Flytrap may have been some kind of support structure for Die Glocke.

A far more plausible theory is that the tunnels and maybe the Flytrap itself were used to test the first helicopters.

Nazi scientists were among the first in the world to develop prototypes of the flying machines.

Scientist Friedrich von Doblhoff began working on the technology in the 1930s and, by 1941, had a working prototype.

A factory which then made the first helicopters was near to the site of the tunnels.

A CGI image shown in tonight's show depicts how one of the first helicopters would have fitted inside the tunnels.

Materials engineer Amma Wakefield said: 'Why design a tunnel that is 36 feet high unless you're planning to have vehicle go in there that needs that clearance or you're building something in there that needs that clearance.'

However, Professor Watson said that the Flytrap is unlikely to have been used as a helicopter landing pad because it was so near to a forest, which would present a serious threat to experimental aircraft.

Guzar said the Flytrap is also unlikely to have been used as a rocket launch site because of the difficulty of getting any projectile through the structure's arches so it could be stood upright.

Abandoned guns, forgotten munitions carts and peeling paint: Inside the eerie military shelters in Poland where children were forced to dig tunnels to help the Nazi military machine. Above: An image taken in 2015

Filmmaker Patrick Ney said in tonight's programme that the tunnels would have been the 'ideal place' for the Nazis to develop their atomic weapons programme without anyone else finding out about it. He spoke of how they put a 'lot of effort' into the mountain facility

Whilst only a small part of the tunnels were ever reinforced with concrete, engineer Brooke Guzar said that because they are built within hard igneous rock, they cold hold themselves up through 'arching action' 

The Flytrap could also have been an unfinished cooling tower, adding weight to the notion that a nuclear testing programme may have been being conducted in the tunnels beneath.

Filmmaker Patrick Ney said: 'We know that scientists went to Adolf Hitler and presented plans to develop the German atomic capability.

'The Owl Mountains complex would have been the ideal place to develop the Atomic programme without anyone else knowing about it. Secrecy on a project like that would have been key.'

He added: 'A little bit like a gambler down to his last chips, they're putting a lot of men, a lot of material, a lot of money, a lot of effort into these mountains, which suggests that they had a card to play.

'It suggests that they were doing something here which they thought potentially could turn the tide of the war.'

The Nazis are known to have begun a programme to develop nuclear weapons. However, progress was hampered by the loss of key scientists to other projects.

Project manager Mr Szpakowski claimed that the atomic weapon dropped on Hiroshima by the US in 1945 was a 'German bomb' or 'at least based on German research'.

Speaking of the strange things he experienced in the tunnels, he said: 'My employee's phone rang… twice. Here deep underground, where it's impossible. Mine also rang.

One final suggested purpose for the Flytrap is that it was a pseudo-religious monument. Heinrich Himmler, who was head of the SS, is known to have had an interest in the occult. It is therefore suggested in the show that the Flytrap as it stands today was the beginnings of a monument to Nazi rule

This is the reason why it has been likened to the far more famous, prehistoric monument Stonehenge, on Salisbury Plain

'So something is going on, some electrical impulses, that make these electrical devices go crazy.'

One final suggested purpose for the Flytrap is that it was a pseudo-religious monument. This is the reason why it has been likened to the far more famous Stonehenge on Salisbury Plain.

Archaeologist and historian Seika Groves said: 'That is the first thing that comes to mind is Stonehenge for me.

'So it could very well be that perhaps it was going to hold some sort of ceremonial or ritualistic presence?'

The SS – the Nazis' paramilitary guard organisation – were the men responsible for guarding both the Flytrap and the tunnels beneath.

Heinrich Himmler, who was head of the SS, is known to have had an interest in the occult.

It is therefore suggested in the show that the Flytrap as it stands today was the beginnings of a monument to Nazi rule.

Highlighting the Nazis' obsession with strange phenomena, Professor Watson said: 'The Nazis did have a programme to actively pursue UFOs. They were also looking for the lost city of Atlantis.

'The Nazis were actually scanning the globe to find Biblical artefacts hoping that all that would imbue Hitler with mythical powers.'

However, fortunately for the Allies, whatever work was being carried out in the tunnels was halted by German defeat in the war.

After the Soviet troops arrived in the region in 1945, Hitler – who committed suicide on April 30 – is known to have ordered the destruction of documentary evidence.

Dr Neill said: 'There was a concerted and sustained effort to burn all available evidence about what the tunnels were used for.'

Secret Nazi Bases is on tonight 8pm on Yesterday (Catch-up on UKTV Play).