Tablinum
In Roman architecture, a tablinum was a room generally situated on one side of the atrium and opposite to the entrance; it opened in the rear onto the peristyle, with either a large window or only an anteroom or curtain. The walls were richly decorated with fresco pictures, and busts of the family were arranged on pedestals on the two sides of the room.
The tablinum was the office in a Roman house, the father's centre for business, where he would receive his clients.
It was originally the master bedroom, but later became the main office and reception room for the house master.