A video has surfaced online of two mysterious dangermen scaling a 70-metre-high bridge over remote New Zealand bush.

The adventurers scale the disused viaduct, located somewhere in the Central North Island, which was built at the end of the 19th century.

Posted on the website of urban explorers Urbex Central and entitled, 'Machineries of Joy', it was filmed by 'Gunner' -- someone who describes themselves on their website as a "film maker, explorer, writer, ethnographer".

A description of the breathtaking feat says the viaduct overcomes a "major valley obstacle in the construction of a national rail line in New Zealand".

Photo / Supplied
Photo / Supplied

"It is over 200 metres long and at over 70 metres high, it was in its time the highest viaduct in the country. The construction took six years due to adverse weather and soil conditions, and a lengthy stoppage in steel production in the UK."

Asked for more details, an Urbex Central spokesman said the climbers "would prefer the viaduct wasn't named publicly".

They added that the climb was "fairly straightforward".