The most difficult Vienna riddles

The four largest cities in Austria are Vienna (1.8 million), Graz (269,000), Linz (193,000) and Salzburg (146,000).

This institution dates back to the time of the Austrian Empire, when Emperor Joseph II made the Prater open to public in 1766. Soon the first snack bars, stalls and bowling alleys opened up on the grounds and the Wurstelprater was born. The best-known attraction is the Wiener Riesenrad, a 64.75 metre tall Ferris wheel.

The Hotel Sacher is a five-star hotel located in the Innere Stadt first district of Vienna, Austria, vis-à-vis to the Vienna State Opera. It is famous for the specialty of the house, the Sachertorte, a chocolate cake with apricot filling. There is also an art gallery in the hotel with works from the 19th century.

The St. Charles Church is a baroque church located on the south side of Karlsplatz in Vienna, Austria. It is widely considered the most outstanding baroque church in Vienna, as well as one of the city's greatest buildings. The church is dedicated to Saint Charles Borromeo, one of the great counter-reformers of the sixteenth century.

Karl-Marx-Hof was built between 1927 and 1930 by city planner Karl Ehn, a follower of Otto Wagner. It held 1,382 apartments. Only 18.5% of the 156,000 m²-large area was built up, with the rest of the area developed into play areas and gardens. At over a kilometre in length (1,100 metres)) and spanning four Straßenbahn (tram) stops, Karl-Marx-Hof is the longest single residential building in the world.

The viticulture in Vienna is operated on an area of 622 hectares of the Viennese urban area (as of 2016). In 2016, 25,341 hectoliters of wine were pressed. This makes Vienna the only major city with significant wine production. A traditional specialty of Viennese viticulture, which has experienced a renaissance in recent years, is the Viennese Gemischter Satz.