An early 20th century scam involved a promise of diamonds and gold, faux investors, fake letters and a quirky typewriter – all centred on what locals call a "bloody big hole".

Nestled among gumtrees on the side of a hill in a national park east of Canberra is a gaping hole that was once at the centre of one of Australia’s most elaborate fraud schemes.

The geological formation known as the Big Hole is 100 metres deep and 35 metres wide.

Located in Deua National Park, it is thought to have formed about 50 million years ago when the roof of a cave collapsed.