A group of Aussie thrill seekers who are no strangers to heights call themselves "weekend warriors" who enjoy "jumping off stuff with ropes" across NSW.
Sam Battin and Timothy Villafuerte are part of the extreme bunch of mates Get The Dice who get together for some social "rope swinging".
The participants are harnessed into ropes that are attached to nuts and bolts anchored into rocks or the ground.
They don't hesitate to dive off high structures like bridges, and freefall for about 10 metres before swinging underneath.
The group's online videos show the men and women leaping off structures - sometimes with backflips, handstands or being thrown head first - at times even without helmets or shoes.
- Adrenaline junkies scale Eiffel Tower without harnesses
- Daredevil plummets from 17th floor and lives to share the terrifying video
A video uploaded to Battin's You Tube channel shows the pair illegally diving off a 149-year-old sandstone Knapsack Viaduct, at the Blue Mountains.
The viaduct is believed to have been built in 1867 to carry trains, then later became a road bridge for the old Great Western Highway.
The NSW Roads and Maritime Services have warned the group of rope swingers that leaping off bridges like the one in the video was not only dangerous, it was also illegal, and could risk damaging the sandstone structures of historical significance, the Daily Mail reported.
“Swinging and climbing on any road bridge is not permitted. It is an offence to damage a heritage item," a spokeswoman said.
"Penalties can be severe for serious offences including large fines and possible jail sentences.
“Attaching ropes and climbing apparatus could damage the sandstone."