Two-horse chariot races (bigae) were held in the Campus Martius, the area of Rome named for Mars, after which the right-hand horse of the winning team was transfixed by a spear, then sacrificed. The horse’s head (caput) and tail (cauda) were cut off and used separately in the two subsequent parts of the ceremonies: two neighborhoods staged a fight for the right to display the head, and the freshly bloodied cauda was carried to the Regia for sprinkling the sacred hearth of Rome.

Alrighty then