There were three parts in a Roman house, which were arranged in the same order in almost every house, although there might have been other rooms attached to them. In front was the _atrium_, partly covered; then came a center space, the _tablinum_, which was entirely covered; and adjoining this latter was the _peristylium_, an open court surrounded by columns. The _atrium_ was the essential feature that marked off the Roman house from that of Greece and other countries of the East. In the primitive houses, and in later times with the poor and the middle classes, this was used for both kitchen and sitting-room, while with the wealthier people it was the reception-room. This contained the family hearth and altar. The street door did not open directly from the street but there was a passage from the street and the door was placed at the end of this passage. Usually there was a square opening in the roof of the _atrium_ for light and in the floor underneath this opening was a cistern for receiving the water that rained in and there were pipes under the floor for carrying off the water. The _tablinum_ was usually separated from the _atrium_ by curtains. This contained the family records and archives; the _peristylium_ was a later addition to the Roman house, coming when Greek architecture became to be used in the buildings. This became the ornamental part of the house, with fountains and flowers and shrubbery occupying the center of the court, surrounded by pillars and open to the sky. There were other rooms, among them being the _alae_, small rooms at the right and left of the _atrium_, and from the _peristylium_ opened the _triclinium_, dining room, the _culina_, kitchen, and the _sacrarium_, chapel. The street door was of wood, having two leaves (a folding-door), moving on pivots, and in private houses opening inward and outward in public buildings. When opening inward the door was secured by a bolt and when opening outward by lock and key. There were but few windows and in general only in rooms above the ground floor. Paper, linen cloth, horn, and mica were used in the windows and glass seems to have come into use under the early emperors. The walls were decorated with paintings. The floors of the primitive houses consisted of clay and then came bricks and tiles and stones and later the houses of the wealthy class had marble and mosaics.