I don't have the luxury of a fisheye, yet! So have to make do with my widest lens, either my 24mm tilt-shift, or the 24-105mm, which is my walk around lens, so it's in all likelihood the one I have on the camera at the time I discover some nice tree roots.

This following image (which to me is just a so-so image) was taken using the 24-105mm lens at 84mm of length, not at 24mm! Why? Because I would have gotten too much crap in the image if I went really wide with it. I tried that out first off and took a few steps back then zoomed in to where I could eliminate most everything from the frame. I also got down nice and low for this one, as suggested by Tony above. My horizon is about two thirds the way up the frame, so that the roots are the stars here. In post-production I darkened off the background and the foreground, then painted in more light along sections of the roots, to give them more dimension.