Mr Castella set a marathon record in 1981 and won gold for Australia at two Commonwealth games. He was also named Australian of the Year in 1983.
Since then, he has become well-known for his work in Indigenous communities and health promotion.
“We as a nation cannot reconcile ourselves with what's happening if we don't do something with Indigenous Australia,” said Mr Castella.
For the past four years, Mr Castella has taken a group of 12 Indigenous runners each year from Australia to compete in the New York City Marathon as part of the Indigenous Marathon Project.
For the people he trains, and the communities they come from, the impact on their lives is long-lasting.
"You ask someone to train for six or seven months to run a marathon from not doing any running and they laugh," said Mr Castella.
"You ask them to do it from some of the remote and sometimes inhospitable places on the planet, and it's mind boggling, it’s almost impossible."
He hopes the project will give birth to Australia’s first Indigenous marathon champion.