Impluvium

Impluvium: (from impluere to rain into; prefix im- in + pluere to rain.) It is the sunken part in the centre of the atrium in Roman dwellings. It worked as a cistern or a tank to collect the water from the compluvium of roof. It is usually made of marble and placed about 30 cm below the floor of the atrium.

Water pours both from the gutter and through the rain pipes and is then collected in the basin in the middle of the atrium (=yard), the impluvium.