This castle cake is made from 2 9x13 cakes stacked on the bottom, and 2 8" cakes stacked on top. I got the idea from various cakes on this site and modified as I found fit.
I started with baking the cakes and letting them sit in the freezer overnight a few days before the party. The next night I frosted the cakes with my homemade buttercream frosting and worked on the towers. The cakes were frosted on their own cake boards.
The top part is frosted on a cake board the same size as the cakes. The towers/turrets are made from ice cream cones dipped in melted white chocolate wafers and then I used the store bought crushed colored sparkly sugar. I found the chocolate was a nice sturdy base to help when constructing the cake.
The regular cones are on the bottom with the sugar cones on the top. To construct the cake I added in a few dowels to the bottom cake and placed the top cakes (including the cake board) on top. I also sharpened one dowel and placed it through the both cakes in the center, later to be covered by sleeping beauty. When placing the towers I used melted chocolate again to help stabilize everything.
For the large tower I also used a few dowels within the upside down cone. But by cutting a little hole in the cake, pouring in white chocolate and then "edging" the cones with the chocolate really helped to stabilize everything.
This cake made it a 20 minute drive sitting on my lap. It took me about 1 1/2 hrs to construct and decorate the cake, and another 1-2 hours previously to frost and prep the towers. Everyone was very impressed and best of all, my 4 year old daughter's jaw dropped when she saw it, that was all I needed.