Of the finished drawing showing the axial section through the building (Adam volume 28/47), Alistair Rowan wrote the following: ‘This handsome sectional drawing is taken on the central axis of the main front. It shows the progress from the heroic space of the entrance exedra through a solemn rectangular hall to an impressive central domed rotunda, with an arcaded lobby at the back of the building. It is worth noting how Adam handles the relative importance of the different parts of the interior: the hall is an understated room with a plain coved ceiling, and the doors to the concert hall and ball room (shown here) have plain pediments above them. The door leading into the rotunda is dignified by a full Corinthian aedicule with a pulvinated frieze and matches the doors in the rotunda itself. This superb neo-classical room bears a close relationship to the architect’s Saloon at Kedleston designed in 1760.’

One of the preliminary designs for the rotunda (Adam volume 1/4) has previously been alternatively attributed by Alan Tait as being for unexecuted assembly rooms in Edinburgh, and therefore dating from the Adam brothers’ Scottish office before they went on their Grand Tours. It is argued here, however, that the density of Roman motifs within this scheme were both informed and influenced by the Adam brothers’ Grand Tours. Moreover, the similarity between this drawing and the Adams’ others for the room (Adam volumes 27/50 and 28/47) is too striking to be ignored. According to Martin Hillman, a Friend and volunteer at St Cecilia's Hall, and currently writing a book on the history of the Edinburgh Musical Society, the subscription to purchase the land on which to build the music hall (later St Cecilia's Hall) was only established in June 1759. As such it is unlikely that either Robert or James would have submitted drawn designs for the building prior to their Grand Tours of 1755-58 and 1760-63 respectively.

The Adam brothers’ designs for the Bath Assembly Rooms were not executed. See scheme notes.