%impluvium%

‖n. [ L., fr. impluere to rain into; pref. im- in + pluere to rain. ] (Arch.) In Roman dwellings, a cistern or tank, set in the atrium or peristyle to recieve the water from the roof, by means of the compluvium; generally made ornamental with flowers and works of art around its birm. [ 1913 Webster ]