Founded around 500 BC, Vienna was originally a Celtic settlement. In 15 BC, Vienna became a Roman frontier city (Vindobona) guarding the Roman Empire against Germanic tribes to the north.
Vienna came under threat from the Mongolian Empire that stretched over much of present day Russia and China in the 1200s. However, due to the death of an important leader, the Mongolian Empire deteriorated and Europe was freed from the threat.
During the Middle Ages, Vienna was home to the Babenberg Dynasty and in 1440 AD became residence city of the Habsburg dynasties from where Vienna eventually grew to become the capital of the Holy Roman Empire and a cultural centre for arts and science, music and fine cuisine. In the 16th and 17th centuries, the Ottoman armies were stopped twice outside Vienna (see Siege of Vienna, 1529 and Battle of Vienna, 1683).
Major tourist attractions include the imperial palaces of the Hofburg and Schönbrunn (also home to the world's oldest zoo, Tiergarten Schönbrunn) and the Riesenrad in the Prater. Cultural highlights include the Burgtheater, the Wiener Staatsoper, the Lipizzaner horses at the spanische Hofreitschule and the Vienna Boys' Choir, as well as excursions to Vienna's Heuriger districts.
There are also more than 100 art museums, which together attract over eight million visitors per year. The most popular ones are Albertina, Belvedere, Leopold Museum in the Museumsquartier, KunstHausWien, BA-CA Kunstforum, the twin Kunsthistorisches Museum and Naturhistorisches Museum, and the Technisches Museum Wien, each of which receives over a quarter of a million visitors per year.
In 1804, Vienna became the capital of the Austrian Empire and continued to play a major role in European and world politics, including hosting the 1814 Congress of Vienna. After the Austro-Hungarian Compromise of 1867, Vienna remained the capital of what was then the Austro-Hungarian Empire. The city was a centre of classical music, for which the title of the First Viennese School is sometimes applied. During the latter half of the 19th century, the city developed what had previously been the bastions and glacis into the Ringstraße, a major prestige project. Former suburbs were incorporated, and the city of Vienna grew dramatically. In 1918, after World War I, Vienna became capital of the First Austrian Republic.
From the late 19th century to 1938, the city remained a centre of high culture and later modernism. A world capital of music, the city played host to composers such as Brahms, Bruckner, Mahler and Richard Strauss. The city's cultural contributions in the first half of the 20th century included, amongst many, the Vienna Secession movement, psychoanalysis, the Second Viennese School, the architecture of Adolf Loos and the philosophy of Ludwig Wittgenstein. Within Austria, it was seen as a centre of socialist politics, for which it was sometimes referred to as "Red Vienna." The city was a stage to the Austrian Civil War of 1934, when Chancellor Engelbert Dollfuss sent the Austrian Army to shell civilian housing occupied by the socialist militia. In 1938, after a triumphant entry into Austria, Adolf Hitler famously spoke to the Austrian people from the balcony of the Neue Burg, a part of the Hofburg at the Heldenplatz. Between 1938 and the end of the Second World War, Vienna lost its status as a capital to Berlin.
In 1945, the Soviets successfully launched the Vienna Offensive against the Germans who were holding Vienna. The city was besieged for about two weeks before it fell to the Soviets. After 1945, Vienna again became the capital of Austria. It was initially divided into zones by the four powers (or the four prevailing nations), and was governed by the Allied Commission for Austria. The four-power occupation of Vienna differed in some respects from the four-power occupation of Berlin: the central area of Vienna had an international zone in which the four powers alternated on a monthly basis. When the Berlin blockade occurred in 1948, Vienna was even more vulnerable because there was no airport in the western sectors. However, despite fears, the Soviets did not blockade Vienna. Some have argued that this was because the Potsdam Agreement gave written rights of land access to the western sectors, whereas no such written guarantees had been given regarding Berlin. The true reason will, however, always remain a matter of speculation. During the 10 years of foreign occupation, Vienna became a hot-bed for international espionage between the Western and Eastern blocs. The atmosphere of four-power Vienna is captured in the Graham Greene novel The Third Man and by the movie which followed.
In the 1970s, Austrian Chancellor Bruno Kreisky inaugurated the Vienna International Centre, a new area of the city created to host international institutions. Vienna has regained a part of its former international relevance by hosting international organizations, such as the United Nations (UNIDO, UNOV, CTBTO and UNODC), the International Atomic Energy Agency, the Organization of Petroleum Exporting Countries, and the Organization for Security and Cooperation in Europe.