Mega Weapons/Ships and Artifical Planets Idea

I would love to see mega weapons kinda like the death star or mega ships that are huge, kinda like the super star destroyer in this pic: http://media.pc.gamespy.com/media/827/827314/img_3871773.html

Also artifical planets that take like 2-3 years to build but can be moved.

Now that the unrealistic ideas are out of the way how about Ground to Space weapons?