Pinacotheca & Bibliotheca
The Pinacotheca, or Room for Pictures, and the Bibliotheca, or Library, are apartments which Vitruvius mentions as common in all the great houses of the Romans: It would therefore surprise the reader, should he find no such rooms in the Palace of an Emperor, who was so remarkable for his love of the Fine Arts. But if we consider that noble Porticus or Gallery, which stretches along three sides of this building above the Cella Servorum and Arcades, extending no less than 21x2 feet in length, and 31 feet in breadth, it is evident that sufficient space was left for apartments consecrated to those elegant Arts, of which Diocletian was so great an admirer.
Towards the East (as we learn from Vitruvius) was the proper situation for the Bibliotheca; towards the North was the exposure most approved of for Pictures; and the west side may have been reserved for an Horreum, a room which Pliny mentions as a repository for statues, bas reliefs, and other curious productions of art. This gallery was divided by the three gates to the palace, and by the stairs on each side of them; but I found the communication had been been preserved by passages formed in the thickness of the walls over the gates, as may be seen by the general sections.
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