What are organ pipes?

A national park near the city of Melbourne in Australia has been given the name Organ Pipes National Park, because of the peculiar geological formation called Organ Pipes existing there. The organ pipes in the above park are a set of vertical rocks which look like the pipes of a pipe organ. These rocks are supposed to be more than 400 million years old, and attract many tourists to the park. The park was established in 1972 on 1.21sqkm degraded farmland.