I think you're wanting to do a spiral cake. It's actually pretty easy, but you do have to watch a tutorial on how to do it to really understand it...I did at any rate!
Here is the one I did...http://cakecentral.com/gallery/2213375/40th-birthdayfirst-marathon-cake-for-man
To me it looks like a 3-tier but it's actually only two.
Google 'how to carve a spiral cake' to get some YouTube videos on it.
I actually joined My Cake School.com to learn. She has the best tutorial on it, but you do have pay to join. She has some pretty good tutorials on a lot of other things too so it was worth it to me. But there are freebies out there.