All fitness levels will be put to the test in the Tower Hill Challenge on Saturday.
Mud pits, climbing walls, ice waters, cross-country running and other obstacles comprise the six or 15-kilometre courses in the State Game Reserve.
Challenge organiser and Koroit Football Netball Club president Steve Hoy is excited for the event, which also includes a 3km children's track.
"We have new challenges and moved obstacles around the course from last year," he said.
"Competitors always say the Tower Hill Tingle and the mud are their highlights.
"I think the ice bath is always a refresher too."
The Tower Hill Challenge allows competitors to venture through the reserve in ways they never normally would.
"Part of the organisation of the course means we clear tracks," Mr Hoy said.
"Parts of Tower Hill which are inaccessible now become accessible.
"It's a win-win for the sport and Tower Hill."
Mr Hoy said the challenge this year had enticed people to come to the south-west and he hoped the event would continue to grow.
"We've had great support from the community," he said.
"Our numbers are up from last year and even though online registration closed on Monday night, we're still encouraging people to register on the day.
"We were lucky enough to get Johns Lyng Group as a major sponsor who's helped us out with promoting the event around Geelong and Melbourne.
"We now have competitors coming from near and far away."
Tower Hill Challenge isn't just for fitness fanatics.
Mr Hoy said the nature experience the challenge provided and the multiple course options made it accessible for the whole family.
"We've had a lot of parents sign up with their kids for the 3km track and many people just want to walk the track to get the experience," he said.
"All obstacles are up to people's discretion and it's not a competition.
"The fun factor is what's really appealing."
All fitness abilities are encouraged to join in the stamina tests.
The event finished in the heart of Koroit at Victoria Park and is followed by music, food and entertainment.
Everyone who competes receives a medallion.
For last-minute registrations, head to Victoria Park before 10am on Saturday, December 7.
For more information and pricing head to the Tower Hill Challenge's Facebook page.
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