The gallery is 60 feet long, and comprises the entire top (second) storey of the higher central portion of Adam’s central block, above the entrance hall and the dining room (later the music room) on the principal storey. Adam divided the room into three by the installation of Ionic screens at the north and south ends, and ornamented the walls with a frieze of urns, tripods, festoons and rosettes (see Adam volume 53/50). There is a barrel-vaulted ceiling for which Adam designed a compartmental ceiling (Adam volume 12/61), but this was not executed owing to a disagreement between the architect and his patron.

The original use of the gallery is not clear, although it has been suggested that it was intended as a viewing platform. The gallery is now used as a museum where some of Adam’s drawings are displayed.