Hotelier Florian Weitzer's latest project – a 1950s concrete block formally home to Austria’s domestic intelligence agency - may be one of the less grandiose buildings of Vienna’s Innere Stadt, but its black granite and sandstone facade, sympathetically preserved by local architecture firm Atelier Heiss, is now under historic preservation, and is no less impressive than the grandes dames it neighbours.

Inside, a large hand-crafted chandelier modelled on traditional designs by Viennese glassworker Lobmeyr hangs above Thonet chairs on the ground floor, and 188 rooms and suites feature gunmetal grey walls, Anglepoise lamps, white marble table tops, dark parquetry and round, leather rimmed Jacques Adnet-style mirrors by Gubi.

There are three dining options; the stately 200 cover dining room serves a modern take on Austrian classics such as veal kidneys and Tafelspitz, the more intimate Gulasch & Champagne is suited to early evening aperitifs, while the Grand Étage rooftop bar sits alongside the pool and has knockout views across to Prater Park in the east. For us the option to sip Mumm champagne from the comfort of a cast-iron art nouveau tub in-suite was too much to resist.