Citadels are the largest of the Military Structures. Citadels do not appear on the lists of Military Structures that protect Non-Military. Clicking on a Citadel returns the message, "This is a super high level military structure, beware." Citadels do not yet launch reprisal attacks.
Occupants: 30-100 Elves, levels 200-1000 (strong chance of encountering a level 200-700 Paladin).
Commonly referred to as "F4" (Fortress Tier 4).