Courtroom (The War Games)

The Second Doctor's trial following the War Game took place in a courtroom. (TV: The War Games)

By some accounts, this courtroom was located in the Capitol on Gallifrey, at the headquarters of the Celestial Intervention Agency. (PROSE: Future Imperfect, Lungbarrow) Romana II once faced Ferain in the court-chamber. (PROSE: Lungbarrow)

Another account indicated the Three were based on the Station, (PROSE: Legacy) which also contained the courtroom of the Sixth Doctor's trial. (PROSE: The Mysterious Planet)

Behind the scenes
Paul Magrs' 2012 fan fiction story The Runaway HiFi  states that the courtroom was in the Tower of Canonicity. A reprint of the story appeared in the Obverse Books 2018 charity anthology A Second Target for Tommy.