One of my favorites scenario games included a Roman marching camp or castra. The Romans built these camps at the end of each day's march.
In the scenario I had a Roman legion facing a Gallic attack. The camp was a nice back drop for the scenario. The Romans relied on a camp at their back. Wisely,
The Romans wanted a safe place to retire to in the event of a reversal on the battlefield. Roman camps were designed to be either square or rectangular in shape.
Ironically American base camps in Vietnam resembled Roman camps.