I am wanting a cake similar to this for my wedding. 

But the company that made this has no contact details anywhere. So I can't ask how the cake is supported.

Any ideas how I could support a cake like this? 

Thanks

You put the supports for the top cake in proper spots in the bottom two cakes... It really looks relatively easy... you would just have to be sure where your supports go ahead of time... maybe even putting a support where the two bottom ones come together underneath the center since it is hidden by the "film strip"...

The reals edges could be covered cake boards or even support plates...

Looks like fun!

As @AAtKT ‍ said, dowel the two bottom cakes in the area where the top cake will be setting...about three dowels (or straws) in each bottom cake.

Thanks very much. I suspected something like that, but wasn't sure. Don't really have much experience with dowels etc. so wanted to get a bit of advice. 

Just be sure you have a sturdy board, not just a circle of fondant, under the top cake to rest on the support dowels.

I would guess that 'reels' are using thickish boards instead of cake - maybe gumpaste but I would probaby use  1/4 to 1/2" thick covered foam boards which then have a covering of fondant or gumpaste.  The two bottom reels are pushed together w/the top one supported by dowels.  I personally would use plastic drink straws - 2 or 3 in each bottom cake.  I've done similar set ups like this.  http://www.cakecentral.com/gallery/i/2158953/red-and-white-wedding-tiers             http://www.cakecentral.com/gallery/i/1271471/haystacks

I made a similar cake and it's like what people have said- dowels under the top tier- at least one on each side in front and back so it doesn't teeter. I used an 8" board under gum paste reels. I tried covering a cake board but it seemed too thick compared for the other reels, so I just hid a smaller one under the reel and it was fine. Can't wait to see pics!