Viennese gourmets prize Steirereck as much for chef Heinz Reitbauer’s daring mod-Austrian menu (think mountain trout seasoned with lime salt, and char cooked in hot beeswax) as for the fin de siècle charm of its Art Nouveau dining room overlooking the river Wien. The restaurant’s enduring popularity, however, meant that despite a renovation a few years ago, diners were beginning to feel somewhat cramped. Steirereck’s recent extension by local architects PPAG looks sets to win over more converts. Occupying what used to be a terrace leading to the children’s playground, the new wing comprises a series of silvery glass pavilions. Depending on the weather, entire panels rise vertically like escape pods on a mother ship to open up the dining room to the park outside. Inside, compact concertina screens – made of industrial timber and curling like lemon peel – section off clusters of tables. All the better, we think, to provide the illusion of serene isolation while tucking into the chef’s tart pudding of quince served with burnt milk and lavender.