The Blue Mountains outside Sydney are remarkable beautiful—but they are not technically mountains. They are the remains of a great plateau that has been worn away until all that is left are cliffs and gorges. From the ground, it looks quite a bit like a mountain range, especially from a distance, but once you reach the flat top, it becomes more obvious that this is a plateau.
The photo below overlooks part of the Jamison Valley, an area known for its beauty, waterfalls, bird life, and great hiking trails. The shot is from my first visit to these lovely non-mountains.