The Atrium or Cavum Aedium was a large apartment roofed over with the exception of an opening in the centre, called _compluvium_, towards which the roof sloped so as to throw the rain-water into a cistern in the floor, termed _impluvium_, which was frequently ornamented with statues, columns, and other works of art. The word _impluvium_, however, is also employed to denote the aperture in the roof. The atrium was the most important room in the house, and among the wealthy was usually fitted up with much splendour and magnificence. Originally it was the only sitting-room in the house; but in the houses of the wealthy it was distinct from the private apartments, and was used as a reception-room, where the patron received his clients, and the great and noble the numerous visitors who were accustomed to call every morning to pay their respects or solicit favours. But though the atrium was not used by the wealthy as a sitting-room for the family, it still continued to be employed for many purposes which it had originally served. Thus the nuptial couch was placed in the atrium opposite the door, and also the instruments and materials for spinning and weaving, which were formerly carried on by the women of the family in this room. Here also the images of their ancestors were placed, and the focus or fire-place, which possessed a sacred character, being dedicated to the Lares of each family.--4. ALAE, wings, were small apartments or recesses on the left and right sides of the atrium.--5. TABLINUM was in all probability a recess or room at the further end of the atrium opposite the door leading into the hall, and was regarded as part of the atrium. It contained the family records and archives. With the tablinum the Roman house appears to have originally ceased; and the sleeping-rooms were probably arranged on each side of the atrium. But when the atrium and its surrounding rooms were used for the reception of clients and other public visitors, it became necessary to increase the size of the house; and the following rooms were accordingly added:--6. FAUCES appear to have been passages, which passed from the atrium to the peristylium or interior of the house.--7. PERISTYLIUM was in its general form like the atrium, but it was one-third greater in breadth, measured transversely, than in length. It was a court open to the sky in the middle; the open part, which was surrounded by columns, was larger than the impluvium in the atrium, and was frequently decorated with flowers and shrubs.--The arrangement of the rooms, which are next to be noticed, varied according to the taste and circumstances of the owner. It is therefore impossible to assign to them any regular place in the house.--1. CUBICULA, bed-chambers, appear to have been usually small. There were separate cubicula for the day and night; the latter were also called _dormitoria_.--2. TRICLINIA are treated of in a separate article. [TRICLINIUM.]--3.