Being the capital city of Austria, 14.99 million tourists visited Vienna in 2016. In 2014, 6.2 million tourists visited Vienna and amounting to 13,524,266 overnight stays. The main markets for tourists are Germany, the United States, Italy, and Russia. Between 2005 and 2013, Vienna was the world's number one destination for international congresses and conventions. In 2014, 202 international conferences were held in Vienna, making it the second most popular congress location worldwide according to the statistics of the International Congress and Convention Association. Its largest conference center, the Austria Center Vienna (ACV) has a total capacity for around 20,000 people and is situated next to the United Nations Headquarters in Vienna. Other centers are the Messe Wien Exhibition & Congress Center (up to 3,300 people) and the Hofburg Palace (up to 4,900 people).
Art and culture had a long tradition in Vienna, including theatre, opera, classical music, and fine arts. The Burgtheater is considered one of the best theatres in the German-speaking world alongside its branch, the Akademietheater. The Volkstheater Wien and the Theater in der Josefstadt also enjoy good reputations. There is also a multitude of smaller theatres, in many cases devoted to less mainstream forms of the performing arts, such as modern, experimental plays or cabaret.
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 Heurigen district Döbling.
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, Bank Austria 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.
There are many popular sites associated with composers who lived in Vienna including Beethoven's various residences and grave at Zentralfriedhof (Central Cemetery) which is the largest cemetery in Vienna and the burial site of many famous people. Mozart has a memorial grave at the Habsburg gardens and at St. Marx cemetery (where his grave was lost). Vienna's many churches also draw large crowds, famous of which are St. Stephen's Cathedral, the Deutschordenskirche, the Jesuitenkirche, the Karlskirche, the Peterskirche, Maria am Gestade, the Minoritenkirche, the Ruprechtskirche, the Schottenkirche, St. Ulrich and the Votivkirche. Modern attractions include the Hundertwasserhaus, the United Nations headquarters and the view from the Donauturm.
Vienna has an extensive transportation network with a unified fare system that integrates municipal, regional and railway systems under the umbrella of the Verkehrsverbund Ost-Region (VOR). Public transport is provided by buses, trams and 5 underground metro lines (U-Bahn), most operated by the Wiener Linien. There are also more than 50 S-train stations within the city limits. Suburban trains are operated by the ÖBB. The city forms the hub of the Austrian railway system, with services to all parts of the country and abroad. The railway system connects Vienna with other European cities, like Munich, Venice, Budapest, Prague, Bratislava, and Zürich. Vienna has multiple road connections including motorways. Vienna is served by Vienna International Airport, located 18 km (11 mi) southeast of the city center next to the town of Schwechat. The airport handled approximately 22 million passengers in 2014. Following lengthy negotiations with surrounding communities, the airport will be expanded to increase its capacity by adding a third runway. The airport is currently undergoing a major expansion, including a new terminal building opened in 2012 to prepare for an expected increase in passengers.