The Rotunde (German: [roˈtʊndə]) in Vienna's Leopoldstadt district was a building erected for the 1873 Vienna World's Fair (German: Weltausstellung 1873 Wien).

[1][a] While the Rotunda stood, its dome was the largest in the world, larger than the Pantheon in Rome.

[b] Not until 1957, 20 years after the Rotunda fell, was a larger dome built: the dome of Belgrade Fair – Hall 1, which is only about 1 m (3 ft 3 in) larger in diameter.

The Rotunde was designed by the Austrian architect Baron Karl von Hasenauer, and was built by the German entrepreneur and bridge builder Johann Caspar Harkort VI [de] and his Duisburg-based company.

The Scottish civil engineer John Scott Russell was responsible for the dome, which was built with wrought iron.

[2] The German engineer and journalist Wilhelm Heinrich Uhland [de] reported that the Rotunde weighed approximately "80,000 hundredweight (Zoll centner), or about 4000 tons", that is, 4,000,000 kg (8,800,000 lb).

Accordingly, the weight of the Rotunde reported by Uhland can be converted into metric units:

The central building of the World's Fair was accepted enthusiastically by the public.

Alexander Girardi performed in the Rotunde on 24–25 May 1885, singing Gustav Pick's new composition, the Fiakerlied, for the first time.

[5][6] In 1898, Emperor Franz Joseph's Jubilee Exhibition [de] (German: Jubiläumsausstellung) was held in the Rotunde.

The "Collective Exhibition of Austrian Automobile Builders" (German: Collektivausstellung österreichischer Automobilbauer), organized by the Austrian Automobile Club [de] (German: Österreichische Automobil-Club), was held as part of the Jubilee Exhibition.

Its former site is now occupied by buildings associated with the Vienna University of Economics and Business, and with Messe Wien.