Runners and riders hit a 20-kilometre trail in farm country at Tocal on Sunday.
Some participants went further, completing two or three loops of the circuit.
The Bunker and Back event had a strong community spirit, as entrants pushed themselves for personal and public causes.
Rutherford Telarah Rotary Club held the event, which supported Hunter Medical Research Institute [HMRI] with its ovarian cancer work through the Jill Emberson Memorial Fund and its Sports Concussion Clinic.
The club's president Gillian Weatherall said the club had made a decision to "be proactive and create our own event".
"It's heartwarming to see the number of people who have come out to do something for the community," Mrs Weatherall said.
She said it was a great opportunity for people to "get out and about" in a time when the pandemic continues to influence society.
Many events have been cancelled over the past seven months, as COVID-19 has wreaked its havoc.
Being outside, the event was deemed safe. It was held on a working farm at Tocal College.
More than 150 people participated. As they navigated the challenging nature of some parts of the course, participants found themselves running past cattle and horses and through creeks.
Race organiser Mick Perriman said the terrain was rugged in parts, especially the first 10 kilometres. "On the mountain, there's great views," he said.
The name of the event comes from the site's history. "There's a bunker out the back of the property used for artillery target practice in its day," Mr Perriman said.
"The bunker is still there, I don't know about the artillery."
Mrs Weatherall said participants had been generous, giving donations on top of entry fees. The event is on track to meet its target of raising up to $8000.