impluvium

An impluvium is a cistern or tank found in the atrium or peristyle of ancient Roman houses. Its purpose was to collect rainwater that fell through an opening in the roof called the compluvium.1

Roman residential architecture often featured interior courts and gardens. The atrium, a rectangular room with an opening in the roof, was a distinct Roman element. Light was typically provided by the atrium or a colonnaded court known as a peristyle. The domus was a common type of Roman house, characterized by rooms grouped around a central atrium, with additional rooms often added at the rear around a peristyle.2