The Pinnacles Desert in western Australia’s Nambung National Park features limestone formations as high as five meters, standing amid windswept sands. How they formed is the topic of some controversy, with several theories competing. The only thing everyone agrees on is that the raw material they were formed from consisted of a gazillion shells that were broken down into sand, and then blown inland to form dunes. As the dunes were later blown away (over tens of thousands of years), they left behind these formations.
This image is the least phallic I could find. If you go to the Pinnacles Desert Wikipedia page (linked above), you’ll see what I mean.
(Photo by Jean Paul Ferrero. Click the image to pinnicate.)