The Twelve Apostles is a collection of eight miocene limestone rock stacks jutting from the water in Port Campbell National Park, between Princetown and Peterborough on the Great Ocean Road in Victoria, Australia.
The nine original apostles were formed by erosion, approximately 10 to 20 million years ago. The harsh weather conditions from the Southern Ocean gradually eroded the soft limestone to form caves in the cliffs, which would then become arches, which in turn would collapse; leaving rock stacks up to 45 meters high.