The elevation of the new gallery building facing the garden is built in Bath stone to match the main façade.  This substantial addition to the west façade of the Palace resembles a garden pavilion and terminates the vista along the main terrace of the Palace.  Its pedimented north front features an arch breaking into the entablature, the design of which is based on that of a building within the precinct of the Temple of Isis at Pompeii.  Drawings for a fanciful reconstruction of this building are in the Royal Collection and the design makes reference to some of the unusual details that they reveal.