This drawing is an imaginative reconstruction of a house in Pompeii.
We are looking at the central axis of a Roman house from the entrance through
the atrium and the tablinum into the peristyle (here hardly visible).
The familia (including both family members and slaves) gathers in
the atrium, which is used as a family room. The tablinum, just
beyond the atrium, is lined with columns on both sides and, when the owner
wanted to use it as a private office, no doubt was shut off from the atrium,
peristyle, and side rooms by the closing of curtains all around.
With the tablinum open, as we see here, there would be an
additional room for entertaining guests.