For centuries refuse and bodies, notably of those perceived to be contaminating the state, wree dumped in the Tiber. Traditional and convenient, this added the insult of denial of burial; the water removed the pollution, and it offered purification against hostile spirits. Disposal via the Tiber was a rejection of disruptive elements, a restoration of order, and a lustration. Topography, convenience, and legal/ritual continuity suggest that the Tiber performed similar functions for the disposal of similarly miasmatic refuse from the games as damnation to the arena, over time, largely replaced normal means of execution. Condemned noxii, pariahs and foes, were killed in a public place as spectacle, the dead were displayed and denied burial, and disposal probably followed traditional lines. Completing a ritual process, the Tiber bore arena corpses ofnoxiiaway from Rome and prevented spiritual pollution and haunting by the souls of the untimely dead, for whose violent deaths the Roman community was collectively responsible.

from Donald Kyle’s Spectacles of Death in Ancient Rome.