They tunneled under it, flew over it, and in its early days even climbed across it. At least 80 people died trying to cross the Berlin Wall over the course of its 28-year existence.But one of the wall's most dramatic breaches was funded almost entirely by NBC News.

The wall went up so quickly in August 1961 that many Berliners found themselves trapped in the Eastern half of the city. In order to help get some of their friends and family out, one group of young Germans and Italians in the West decided to build a tunnel.

After finding a factory building on a West Berlin side street and a basement just 100 yards or so away on the eastern side of the city, they set to work in May 1962 building what has come to be known as Tunnel 29.

The going was tough: the ground was clay, their funds were low, the risks the ground would shift were high. Friends who had attempted a tunnel nearby had almost died when it collapsed, and persuaded the group that they needed more money and material to shore up their underground passage.

As they dug and dug, there was an NBC News producer struggling to find a way to tell the stories of Berliners trapped by the wall and attempting escape. One day, one of the journalists in NBC News' Berlin bureau came to Executive Producer Reuven Frank with an idea.

"I've got a tunnel," journalist Piers Anderton said. Neither he nor Frank could have imagined the drama to follow.

In June 1962, NBC News struck a deal through a local film company which would mean more money up front for the group working on Tunnel 29. The network agreed to finance the entire escape tunnel, paying 50,000 Deutschmarks — or roughly $150,000 today — for exclusive film rights of the dig.

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The cloak-and-dagger project was steeped in secrecy. Outside of a small production team in Berlin, only the president of NBC News and his assistant knew the details. Corporate lawyers were kept in the dark, the project was never mentioned over the phone and funds were dispersed "outside the NBC channels."

Those funds went to tools, food and even an underground rest area for the group of over 40 tunnelers — mostly students — to toil through the day and night.

The group suffered serious setbacks from flooding and faced monumental risks throughout. With one in six East Germans working for the secret police, the prospect of imprisonment or even death if betrayed was always in the minds of the diggers and camera crew.

What the tunnelers suspected — but did not know at the time — was that that one of their volunteers was an agent. To throw off the secret police they changed the tunnel's exit point, even though it meant more digging and supplies courtesy of NBC News.

By late September 1962, the leaking tunnel was ready for its first escapees. After passing coded messages to the East over NBC News' short-range radios, the first fugitives were brought down into the tunnel.

The NBC News team — mostly lying on their backs — captured some of the most dramatic and moving footage of the Cold War, filming organizers shepherding more than two dozen men, women and babies to the West, where they arrived covered in sand and mud. One digger was reunited with his wife and new baby who came over through the tunnel; another female escapee reportedly wore a designer Dior dress for her escape in order to arrive looking her best.

While the organizers had hoped to use the tunnel repeatedly, it had to be abandoned after two trips due to the leaks.

The story was told in NBC News' documentary "The Tunnel," which was meant to air on Oct. 31, 1962 but was held after NBC came under pressure from the State Department not to exacerbate tensions after the Cuban missile crisis.

ARCHIVAL VIDEO: Watch 'The Tunnel'

“They tried like hell to keep it off the air,” producer Frank recalled.

The program, which eventually aired on Dec. 10, went on to win three Emmy awards, and generated great controversy over a U.S. network's move to fund such a political project.

It's thought that around $20,000 of NBC News' money went into building Tunnel 29. The remainder of the cost was reportedly shared by the group who masterminded the incredible escape in the face of unspeakable odds — and ever-present danger.

As the tunnel was in its final yards, 18-year-old Peter Fechter was shot trying to cross into the West. He was left to bleed to death at the wall. Those digging underneath the wall pinned Fechter's photograph to the entrance of Tunnel 29 as a reminder of the price they might pay.

The tunnel, though, was only discovered by the secret police when it collapsed — 11 days after escapees crossed over. And the suspected secret agent? Turns out he existed — but was kept in the dark about the actual escape and the tunnel's changed exit point, allowing the group to pull off one of the greatest escapes of the Cold War.