An Austrian pilot has set a new world record after flying a hot air balloon 206 metres underground in Croatia.
Ivan Trifonov successfully landed a balloon at the bottoms of the Mamet Cave in Obrovac in the Velebit nature park.
The flight took 25 minutes and Trifanov flew a smaller-than-usual balloon that meant he had to sit on two gas cylinders framed by iron pipes rather than a traditional basket.
According to Stuff.co.nz, the entrance to the cave was just 60 metres by 70 metres.
Trifonov, who holds four Guinness World Records for hot air ballooning and is the first person to balloon over the South and North Poles, told the Guardian: "I don't believe this is going to be repeated by anyone ever again."
There's a challenge if ever we heard one.
Ivan's flight was supported by the Croatia Tourist Board, who uploaded the video to YouTube and wrote: "Exactly 10 years after the recording of Felix Baumgartner's base-jump in the Mamet Cave went around the world, this abyss on Velebit Mountain became the scene of another incredible daredevil venture.
"Ivan Trifonov, a seventy-year-old Austrian with a Croatian passport, was the first man to try, and succeed in flying a hot-air balloon underground.
"For flying underground, Trifonov had to use a hot air balloon specially designed for this unusual, and probably unrepeatable venture. His balloon was smaller than usual, and the brave pilot set on two gas tanks linked with steel pipes, instead of a basket."
Wonderbra hot air balloon crash-lands in residential street in Surrey
Three tourists die and 22 injured in hot air balloon crash in Turkey
Hot air balloon crash-lands on Bath city centre road