When Julio Caesar built 2 walls during the Battle of Alesia: one to encircle the Gauls under the leadership of Vercingetorix and an outer wall to keep out relief army.
But by doing so, Caesar and his 60,000 army were hemmed in with nowhere to go: they had to fight to the death.
But Caesar prevailed in what is considered one of the greatest military victories in history. It's all on Netflix. Fascinating stuff.
I have been to Rome and seen the spot where Caesar was murdered. And of course the magnificent Pantheon and Coliseum still stand.
Every modern stadium uses the design of the Coliseum to usher spectators in and out at different levels.