The Organ Pipes describe a rock formation that can be seen on the trail that leads down from the car park at the top of Mt. Wellington. Mt. Wellington makes an excellent bushwalk and if you have two cars, you can leave one up at the top and the other one further down the road so you don't have to make a return trip.
The cache is located about 1.5-2.0 km down the trail from the upper car park and at time of hiding contained log book, pen, assorted business cards, and a few other goodies. From the cache site continue down the trail and hang a left at the intersection to get a better view of the organ pipes.
Partial spoiler: This particular geocache uses my standard international cache container. You can learn more about these containers here.