The rainwater that entered through the central opening in the atrium or compluvium was gathered in a pond paved with mosaic, the impluvium, under which there must have been a cistern. Over time, when the water supply system was refined and the cistern was eliminated, the impluvium became a decorative feature. In the middle of it there probably used to be a fountain that was fed water through a lead conduit, which is currently missing. It is paved with a mosaic made of white and black marble tesellae. The one visible today is a reproduction; the original is in the Archaeology Museum of Catalonia in Barcelona.