When the Kunstkammer reopens on Friday, Vienna will come face to face with the extraordinary wealth and downright eccentricity of its first family. For 640 years, the Habsburgs, a family of aristocrats originating in modern Switzerland, had run a vast Austrian empire that suddenly fell apart at the end of the First World War, in the pan-European cataclysm known as the Fall of Eagles.
The Kunstkammer (literally "chamber of art'' but often taken to mean "room of curiosities'') is a collection of unusual artworks acquired by different Habsburg rulers over hundreds of years. Many royal families in Europe put together these collections, but the Habsburgs did it first and did it best. Emperors such as Ferdinand I and Frederick III - and various ambitious archdukes along the way - built up several Kunst and Wunder Kammers: treasuries of beautiful works of art augmented by oddities from the natural world.
It was Rudolf II (1552-1612), Habsburg Holy Roman Emperor, who put these various collections together in the first internationally famous Kunstkammer, assembled at Prague Castle. Visiting diplomats and VIPs would be shown the family's collection as a mark of favour, but also as proof of what Habsburg wealth could buy.
In 1891, Emperor Franz Joseph, one of the least intellectually curious monarchs in European history, rationalised the collection by moving the Mexican headdresses to Vienna's Museum of Ethnology and leaving the humorous drinking vessels and portraits of people with horrific disabilities in Ambras Castle near Innsbruck. The remaining 8000 pieces of art were then moved into the emperor's new Kunsthistorisches Museum, just across the Ringstrasse from Vienna's Neue Burg palace.
I had a sneak preview of the new Kunstkammer last week. The entire collection was crammed in here in 1891, piled up on shelves with only natural light for viewing. It must have looked like a jumble sale, albeit one awash with gold, diamonds and rubies. No wonder that, in 2002, the museum withdrew the collection and embarked on a new way of displaying just a fraction of it.
Eleven years on, just over 2000 pieces are on offer now in tall, brilliantly lit glass cabinets that throw the rest of the museum into shadow. Pride of place goes to a 17th-century unguentarium (oil container) carved out of one single, 2680-carat piece of Colombian emerald, and to a silver automaton clock featuring the goddess Diana riding a centaur, designed to move across a table surface on the hour. There's also a tankard made from the tusk of a narwhal embellished with 16 rubies and 36 diamonds, and a silver writing box with 10 compartments, each decorated with life-size silver insects.
There are quite a few objects made from natural exotica too, such as a goblet fashioned out of an ostrich egg supported by red coral, and a tortoiseshell drinking flask in the shape of a heart that's trimmed in Indian silver. Among the more grotesque objects are Commedia dell'Arte figures in Murano glass and three painted carvings depicting a young man, young woman and an ancient hag standing back to back. (What they represent, no one knows.) Far too many landscapes are rendered entirely in precious stones and it seems almost anything can be carved out of ivory, but taste is something of an irrelevance in the Kunstkammer.
Many of these objects were made simply to see if such ideas were possible. One of the best known is a salt cellar by Benvenuto Cellini. This golden cruet set depicts Neptune and an Earth goddess seated naked, a box for pepper near her right hand and a ship containing salt in his. Cellini was told by his original patron that the design was impossible to realise, but in 1543 he found a Habsburg relative willing to put up the necessary gold.
Today, when so much is available on the internet, it is difficult to imagine just how important it was for a ruler to gather every kind of object under his roof. Cabinets of curiosities were not just for prestige, they were for knowledge, the kind of knowledge from which power derives. According to Sabine Haag, director of the Kunstkammer collection, Rudolf II instructed his agents across Europe, Asia and the Americas to bring him objects of unrivalled quality, exclusivity and rarity.
In the days before we understood the concept of curating a collection, the Habsburgs collected with zeal, building a baggy but comprehensive picture of the world at its most extreme both beautiful and ugly.
The Habsburgs themselves are commemorated in many kinds of portrait. Charles V is depicted armless, just a bronze head stuck in a suit of armour, as was the 16th-century fashion. Joseph I is represented by a marble Action Man on a horse, crushing a vanquished Fury beneath its hooves. Ferdinand III is a life-size painted waxwork.
An hour and a half in the 20 refurbished rooms proved overwhelming. I found myself awestruck by the craftsmanship, amazed by the sheer wealth of Habsburg patronage and yet also reduced to hilarity at times. Why lavish an enamelled gold stand, lid and intricate clasp on a bezoar stone from the intestines of a cow? Why patronise the unknown artist who created a beautifully glazed figure of a naked woman sitting on a giant hedgehog? Because we can afford anything; that seems to be what the Habsburgs are telling us.
As I step outside the Kunsthistorisches Museum, the same level of opulence and eccentricity seems to envelop the rest of the historic city centre. Vienna is a paradox, a capital city built to run an empire that stretched from Belgium and the eastern territories of France, through Holland and modern Germany as far as Poland, Hungary, Slovenia, Croatia and Italy, but that now runs a country smaller than Iceland or Serbia. Artists of all kinds flocked here for centuries. So much energy and ambition was bottled up within the city walls (the route of the modern Ringstrasse) that no wonder Vienna turned into its own Kunstkammer.
The plague monument in the Graben is one of the most grotesque celebrations of deliverance. Emperor Leopold I's reaction to the great pestilence of 1679 was firstly to flee the city and then to declare he'd erect a Pestsule (plague column) when the all-clear was given. The monument tactfully shows Leopold in prayer rather than flight, while Plague herself an old hag tumbling to her destruction is truly grisly.
The Kaisergruft, beneath the Capuchin Church, is something of a rarity: a city-centre crypt where you can walk in and view all the Habsburg tombs since 1619. There are 107 coffins and five urns containing hearts. Charles VI has the scariest sarcophagus: the emperor in all his regalia with the head of a skeleton. Joseph II (Mozart's patron) has the plainest coffin, but the entire vault abounds with gilded skulls, like something out of a Terry Gilliam film.
The curious nature of Vienna did not end when the city wall came down. In the 19th century, the Viennese were able to indulge their love of coffeehouse life to the full with cafs dotted around the Ringstrasse. As the owner, Herr Querfeld, told me when I parked myself at Caf Landtmann for the day, coffeehouses were never about the coffee. That first cup is a down payment on your table rental. Because most Viennese apartments were too small to entertain in, social life was and still is conducted in the coffeehouse. At Caf Central nearby, this is commemorated by a life-size waxwork of the poet Peter Altenberg sitting at one of the tables. Altenberg was renowned not just for his verse but also for never going home.
At the moment, many of Vienna's coffeehouses are staying open all night as this is Fasching, the season of the balls all 450 of them, including 17 in the Hofburg Imperial Palace. It's a tradition kept up by Vienna's twenty-somethings, that you do not go home at four in the morning but go straight to a coffeehouse for breakfast. The fact that thousands of young Viennese practise all year to be able not just to waltz but minuet in ballgowns and tails says something else about both the city's attachment to its Habsburg past and its sheer idiosyncrasy. Nowhere else in the world maintains such a 19th-century tradition in its entirety.
The city also has more than its fair share of odd regulations. Not everyone is aware why there is an open space running between the Coburg Bastion and the Stadtpark. This long, empty rectangle was originally called Gartenbaupromenade but was renamed Theodor-Herzl-Platz in 2004 after the father of Zionism. But the space is actually there because when the city walls came down, the Habsburgs promised the Coburg family that no buildings would obstruct their view of the countryside from their palace atop the bastion. Consequentially, when plans for the new Marriott Hotel were drawn up in 1983, they had to be shifted to the left to maintain the palace's view of Stadtpark.
At the other end of the social spectrum, who can doubt the influence of Adolf Loos's odd little American Bar off Krtnerstrasse? It's a tiny, stripped-down space that the architect designed in 1908 as part of his reaction to the florid historicism of Viennese architecture. Orson Welles drank here during the filming of The Third Man and Hollywood stars make a pilgrimage here when in town. Nevertheless, the current owner, Marianne Kohn, isn't above throwing any of them out if they break her "no photographs'' rule. By being so completely and utterly itself, Loos American Bar has recently earned the ultimate form of flattery: imitation. This month a reproduction opens in New York's trendy Meatpacking District.