Historians disagree as to whether there were ship battles in the Colosseum or not. We do know massive basins were dug on the banks of the Tiber for the battles. In theory it would have been possible to hold a Naumachia in the Colosseum. Some supporters of the theory point to the pipes discovered under the Colosseum as evidence. Titus is credited to having held a Naumachia within the walls of the famous amphitheater.