ok, I did this cake with 24 hours notice and then they asked to have the cake delivered 1.5 hours earlier than original time. I really needed that last hour and a half to add the detail that would have taken this from cool to totally fabulous but the customer liked it.
I'm not sure if you want to do a 3d Eiffel tower cake or a gp Eiffel tower, but here is how I did this cake.
I started with an 8 inch square cake, a 6" cake, and two 4" cakes. I filled and stacked them without the crumb coat. I used dowels like you normally would to stack the tiers. Then I center doweled the whole thing.
I have the ateco 14" knife, which is my most favorite tool in the world and worth every penny http://www.amazon.com/Ateco-1316-Cake-Knife-Blade/dp/B000KEUKPG
I carved at an angle starting at the top of the 6" cakes to the bottom of the 8 " cake. I left the 4 inch squares un-tapered.
Then I covered the whole thing in white BC. I cut rectangles for the bottom and used a 2.5" round cutter to cut out the bottom arches, applied to cake side and trimmed the fondant on the cake to get the angles right.
Then I cut 1 inch wide strips of fondant and placed vertically on cake, while it was still very soft it was easy to bend to get the exact curve.
I used 1 inch strips for the horizontal pieces, the very top piece is fondant too. I painted the whole thing with vodka and silver dust.
if I had the extra 1.5 hours I would have piped in black RI all the detail metal work on top of the silver fondant.
you can pm me with questions if you have any. This cake was so much easier than I would have thought.