What is "gesolei"

The GeSoLei was the largest trade fair in Germany during the Weimar Republic. It attracted 7.5 million visitors. The name was constructed from an abbreviation of abbreviations of the German words for public health (Ge), social welfare (So), physical exercise (Lei).

Surviving features of the event include the Tonhalle which at the time of its completion was the largest planetarium in the world, built by Wilhelm Kreis