In particular , in the modern Regola there was the Trigarium , the stadium where the riders of the triga ( a cart with three horses ) used to train .
During the Roman empire , the area belonged to the Campus Martius .
In the modern Regola there was the Trigarium , the stadium where the riders of the triga ( a cart with three horses ) used to train .
During the Roman empire , the area belonged to the Campus Martius .