The Prunksaal is the imperial state hall of the Austrian National Library, built for Emperor Karl VI by Fischer von Erlach in the 1720s. It is one of the most magnificent baroque library interiors in existence — a single barrel-vaulted hall 80 metres long, lined with walnut bookcases and ringed by an upper gallery, crowned by a frescoed cupola.
The library still uses the hall but visitors are admitted as a museum. Globes from Prince Eugene's collection sit in the centre. Often quieter than the major painting galleries, and arguably as beautiful. Entry through the Josefsplatz wing of the Hofburg.