The 2000 Year Epic Campaign
Today it lies in ruins.
Session #15 (3rd Era) – The bronze dragon, Kimerth, mentioned that the Red Pillar in the Cerioth Pillar Facility leads directly to a place called The Citadel, where they raise and train their dragonborn army.
Transition from 3rd to 4th Era – Hatred and disappointment of the Empire came to a head after the Third Era ended and the Citadel, which long stood for discipline and training for the Brotherhood, was destroyed by freed dragonborn ex-soldiers. Today it is in ruins, buried under stone.