Aethelburg is a fortress that relies more on it's advantageous placement rather than sheer might of its reinforcements.
The walls are made of huge bricks and reinforced with Steel. Manned by crossbowmen, archers and musketeers.
In the middle of the city and at the edges are many Grand Balista towers, meant to shoot down big aerial threats. With their size being close to 100 feet and their projectiles heavy enough to have to be loaded by cranes - they are able to tear apart a Wyrm in a single shot.
On the walls there are numerous catapults, operated by crews of several infantrymen - shooting heavy boulder projectiles at enemies below.
In the middle of the city there are a couple of collosal trebuchets, reaching 300ft in height. They are crane loaded with fittingly collosal boulders, able to send them miles away - used to target large clusters of enemies approaching the walls.