Sorry for the delay, but let's get this month started!
Whether it is held aloft by turbines, balloons or a hundred dragons, there are clearly many ways to go with such a concept... starting with the technology of the age in which the fortress exists. Whether the materials are steel, wood or stone, all that needs to be clear is that this behemoth is airborne and impressive in both its defenses and weaponry.
Theme: Sky Fortress
Edit: winners announced!