A feature of later houses in ancient Rome, so often found in connection with the atrium that it may have been an early addition to it, is the tablinum, the wide recess facing the front door. The origin of the tablinum, and the way it was used, alike in earlier and in later classical times, are uncertain.
It may have been originally meant for merely temporary purposes, being built of boards (tabulae), and having an outside door and no connection to the atrium. However at some early point the wall between was broken through. When this was once done and its convenience shown, the partition wall was removed. Varro explained the tablinum as having been a sort of balcony or porch, used as a dining room in hot weather.
The term tablinum was derived from the material (tabulae - meaning planks) of the "lean-to," from which, perhaps, it developed. Others think that the room received its name from the fact that in it the master kept his account books (tabulae) as well as all his business and private papers. This is unlikely, because the name was probably already in use before the time when the room was used for like this. He kept in the tablinum also the money chest or strong box (arca), which in the old times was chained to the floor of the atrium, and used the room as his office or study.
View of Tablinum from the Atrium.
In its position it oversaw the whole house, as the rooms could be entered only from the atrium or peristylium, and the tablinum was right in the thick of them. The master of the Roman house could gain complete privacy by closing the folding doors which cut off the peristylium, the private court, or by pulling the curtains across the opening into the atrium, the great hall. On the other hand, if the tablinum was left open, the guest, upon entering the ostium, would have had a lovely view, seeing at a glance all intimate details of the house. Even when the tablinum was shut, free passage from the front of the house to the back was possible through the short corridor at the side of the tablinum.