Castra

• Castra was a Roman Camp, Marching Camp or Fortress, whereas a Castellum was a Roman Fort. These are the definitions that are followed by Classical Scholars.
• The Castra could be either a square or a rectangle and was divided into four equal divisions by two intersecting roads. It was surrounded by four walls with gates and a defensive ditch.

The Roman Fort Grid Plan

• Via Principalis
  • In a Fort, the north-south Cardo Maximus was called the Via Principalis.
• Gates
  • The Via Principalis had a north gate and south gate, the Porta Principalis Dextra (Right Principal Gate) and the Porta Principalis Sinistra (Left Principal Gate).
  • Each gate was fortified with two towers, but whether it was north or south depended on which direction the Praetorium (Base commander’s house) was facing, which could vary.
• Via Praetoria
  • This was the east-west equivalent of the Decumanus Maximus, and intersected the Via Principalis creating four equal divisions of the fort.
• Gates
  • The Via Praetoria had an east gate and a west gate, the Porta Praetoria (Main gate) and the Porta Decumana or Porta Quaestoria (Supplies gate).
  • A Legion marched in via the Porta Praetoria and lined up in the Principia (Parade Ground) in front of the Praetorium (Commander’s building). The Standards of the Legion were placed on display here.
• The Principia
  • This was a central square, similar to the town Forum, which was the Parade Ground and held the Praetorium and officers quarters.
• The Praetorium
  • This was the Base Commander’s Building, where he lived and conducted business.
  • When he stood outside his house, the Porta Principalis Sinistra was to his left and the Porta Principalis Dextra was to his right. Ahead of him was the main ceremonial entrance to the fort, the Porta Praetoria.

Legionary Fortresses of the Roman Empire

• The Ruins of many Roman Forts around Europe can be visited and the outline of their streets and buildings are still visible.