Some years ago I walked into a second hand book shop and I bought a Star Wars Cross sections book. In the center stood the Droid Control Ship. It blew my mind and I knew I had to build it.
I used almost 30000 parts. Lots in the center globe that I build with the aid of a building program that I found on the web. 3500 tiles to cover the outside structure. Lots of Technic parts to make the inside frame, so I could move, lift and take it apart without breaking it. The technic parts are joined left/ right and top / bottom, resulting in a firm and solid almost selfcarrying structure.