If there is actually a way to change to that view at a whim, I'd have that persons babies. I've only seen the view twice on Paskil and it's amazing seeing the mine system.
This is actually super easy to do. Step 1 is get GIMP (or if you have photoshop, use that)
Make sure minecraft is not running.
Type appdata in your start search bar for windows. One of the results should be a folder named appdata, go in to it, then roaming, then .minecraft . Next there is a .jar file you can open in winrar in there, that has a whole bunch of stuff in it. find terrain.png, and drag it to your desktop. Copy it somewhere you'll remember(to make a back up). and then right click and select "edit with gimp" youll need to zoom in, but find the two or three panels that make up dirt. Rectangle select that area, and take your eraser to it. Now, save the file (making sure it is still terrain.png) and drag it from your desktop back into the minecraft.jar directory. It ask if you wanna replace the file, hit yes. Load up mincraft, which now has invisible dirt, letting you see forever it almost every diretion under you. Just drag the backup into the .jar when you want it back to normal
I made a custom map using that method, and built this.
You can see the invisible texture effect where the invisible sand touches the star. Edited, Oct 9th 2010 8:04pm by Tarub