Most often, the deliberation room is adjoining to the courtroom.
This is where the court and the jury go to take a decision, together, on the case.
On this sketch, we see on the table the urn used to draw names at random to form the jury.
No one but the presiding judge, the assistant judges, and the members of the jury has the right to enter while the jury is deliberating. Moreover, anyone wishing to enter or to leave the room must ask the presiding judge’s permission.