Floating Star Shaped City Sized Fortress Idea 

Appearance: https://upload.wikimedia.org/wikipedia/commons/a/a2/Palmanova1600.jpg Edit-As pictured if the gaps were filled with walls and gate houses

Defenses: Force Field, Cannons, Artillery, AA guns, Machine Gun nests, Arc Throwers, Flame Throwers, Archers, Electric Fences, Burning Tar and Oil, Murder Holes and Arrow Slits, etc. 

Main Structure Materials: Titanium, Souls, Thin layer of lead

Buildings and Spaces: Armories, Training Area, Cathedral, Keep, Library, Vehicle Parking, Landing Pad, Main Square, Teleportation Pad Various Walls and Gatehouses, etc. 

Other Notes: The Core reactor is guarded by an Anti-Life Shell Spell, with walls, floors and ceiling made from Adamantium, and enchanted to be teleport proof. Can be self destructed with a five minute timer.     

[@thewizardguy]