The atrium was of the tetrastyle type reminiscent of such atria in Pompeii and Herculaneum. The roof which sloped down inside, was supported on four columns or pillars standing in the corners of a rectangular pool (impluvium) revetted with marble slabs. Light entered through an opening (compluvium) in the centre of the roof. Rain-water was gathered in the pool beneath. Any surplus water was drained through pipes into the storage cisterns. Matching the four columns or pillars supporting the roof of the atrium were decorative pilasters set in pairs on the northern and southern walls of the atrium. The walls were decorated with figural paintings, traces of which have been preserved in the eastern end of the room. Contrary to earlier Italian tradition, the atrium of the Villa of Theseus did not communicate with side rooms, but only with the eastern portico of the main peristyle court. On the floor of the atrium there was a geometric mosaic, the key motif of which was a red-claret maeander on a light background. The mosaic, which was used over a long period of time, shows evidence of repairs, especially near the entrance. Of interest is the fact that in repairing the mosaic in antiquity specialists introduced completely new patterns which had nothing to do with the original decoration. This created the impression that a new carpet with different motifs had been placed on top of the old threadbare one. The deep niche in the western part of the atrium probably contained some statuary.