This is a Princess Castle Cake I made for my niece's 3rd birthday. She was having a Princess theme party, and as I was searching for ideas I stumbled across this site (which I absolutely love!).
I started out by baking 3 cakes - each 9x13 size. I used two for the base of the cake. I used whipped icing, which can be purchased from Sam's club, and colored it a light pink. Then I cut 4 squares of equal size from the third cake. Ice the top of two squares, and then place the other two pieces on top of the iced squares. Carefully place the squares on the back corners of the cake for the towers. Carefully push several dowel rods (cut to proper size) down through the squares into the cake base. This will help ensure that they stay in place.
Then finish icing the towers with the pink icing. Using darker pink icing, draw doors windows on the side of cake and towers. Fill in with blue icing. Ice 4 sugar cones, then roll them in pink sugar crystals (easily purchased from a craft store). Draw 4 flags from pink construction paper, and glue them to toothpicks. Insert the toothpicks into the tip of the sugar cone. Place sugar cones on top of each tower, and in the front corners of cake.
I used sugar cubes to create a wall around the cake and towers. I finished it off by using a Cinderella dress up magnet that I found at the dollar store; I wrote on this. My niece loved it!!
I also made a Cinderella cake to go with the castle. I baked a cake in the Pampered Chef batter bowl. But you can use any oven safe bowl to make a cake that becomes the "dress". I couldn't find a Cinderella barbie,so I bought a blond doll cake pick from craft store, and using a hot glue gun put her hair up and glued on blue ribbon. I used white fondant that I colored blue for the dress. Roll it out to the desired size,and smooth over cake base, crimping icing as needed to make folds in the dress. Place doll pick in center of cake. I used fondant to create the top of Cinderella's dress also. Then I used blue buttercream icing and piped "lace" on the bottom of the dress, and for sleeves. Then I used pearls around the lace.
It could have been neater, but my niece loved it; it was worth it!