I made this map for a contest. They were looking for a flying tower. I also did a version of it on the ground in a winter scene.
The Tower was made in DundJinni with art that is mostly stuff I made, all except for the Ballistas. The flying rock and the out-of-focus background is a ground scene from cgTextures.com

Flying_Tower_Bogie.jpg

FlyingTower-grounded_bg.jpg