The Headquarters Building (Principia) is in the centre of Roman forts.
This is the largest building in the fort. The battle standards of the military unit would have been kept here, the strong room with pay and a shrine to the gods. The building would have comprised a courtyard, a great hall and then a row of rooms for the standards, shrine and pay.
Entry to the Headquarters was through an enclosed courtyard surrounded on three sides by a covered walkway, the column bases for which can still be seen today in many forts. In the corner of the courtyard, there is a small water tank which would have supplied water for religious ceremonies and rituals.
The sunken room at the centre was the most important. This was the strong room which contained the garrison’s funds, above which was a shrine housing the unit’s standards.
- Principia Headquarters of the 6th Legion in Bulgaria