The Vienna State Opera has been provoking strong opinions since before it even opened. When it was completed in 1869, critics called it boxy and said it looked like the box the nearby Hotel Sacher arrived in. The Viennese nicknamed it their "sunken treasure" because it sat a full metre below the road. The two architects were so devastated by the public mockery that one took his own life. Neither lived to see the inaugural performance, attended by Emperor Franz Joseph and his consort, Sisi.

Then came the Second World War. Allied bombing reduced almost the entire building to rubble. Only the facade survived intact.

VoiceMap's Ringstrasse tours use the Opera House as a starting point, tracing how Franz Joseph's 1857 decree swept away Vienna's medieval walls and replaced them with a boulevard of grand institutions, explaining what each building reveals about Habsburg ambition and its aftermath.