A kind thank you to Margaret Morgan of Sydney, Australia for sharing today's image. You can see Margaret's preferred crop of this image on this page, but she gave me permission to select a different crop for one of the standard sizes I use for BPotD (so thanks again). I enjoy Margaret's web site quite a bit (since I seem to agree with her on many things), so you might like to visit it as well: Margaret Morgan. Much appreciated, Margaret.
The common name for this orchid is yet another of those lateral-thinking-required misnomers ̵ rock lily. I suppose it is relatively easy to see a superficial resemblance to a lily inflorescence when looking at the mass of flowers. A closer look at each individual flower, however, reveals it is indeed an orchid (and to be fair, some sites do suggest “rock orchid” as a preferred common name).
The “rock” part of the common name is entirely fitting, however. Dendrobium speciosum is often found growing on rocks (hence it is a lithophyte), though it can also be epiphytic (growing on other plants). It is known as one of the showiest orchids in the world, as I'll assert is well-detailed by Margaret's second photograph.
Two excellent pages worth investigating if you'd like to learn more are Dendrobium speciosum from the Association of Societies for Growing Australian Plants and the Dendrobium speciosum complex from the Australasian Native Orchid Society.