Water in the Coliseum FWIW I watched a program on the History channel a couple of months ago the focus of which was a chemical study of the makeup of the plaster used in the Coliseum and examination of the flooding and drainage facilities the Romans had built into the coliseum The program concluded that the plaster used contained small but notable amounts of the substance that the Romans used in aqueducts for waterproofing but not enough that it was designed to be a permanent feature of the arena It also concluded that the coliseum could have been flooded overnight and that it was probably built with it being flooded shortly after completion but not again after that in mind I can t find in the brief search I ve just done anything I can cite so I m not going to put it into the article yet but I d say that the section relating to the flooding of the coliseum is probably slightly out of date