Ahornstraße 15a, Historical building in Steglitz-Zehlendorf, Germany.

Ahornstraße 15a is a two-story villa in Steglitz-Zehlendorf with a single-story extension, plastered facade, and round windows on the first floor that have been bricked up. The building, vacant since 2013, contains a basement with former performance spaces and rehearsal rooms for musical activities.

During the Weimar Republic, this building served as the main meeting point for the Social Democratic Party and Reichsbanner to organize resistance against the National Socialists. After the war, it housed the Grand National Mother Lodge between 1946 and 1957 before becoming a cultural venue for young people.

The building's cultural life began in May 1960, when youth senator Ella Kay opened West Berlin's first youth club here, the jazz-saloon, serving drinks herself at the opening. Funded by the Berlin Senate and run by Berliner Jugendclub e.V., it used jazz to draw young people off the street; until the Wall was built in 1961, teenagers from East Berlin also came. Renamed PopInn in 1967, it hosted progressive rock concerts, including Agitation Free in November 1974, Space in March 1975 and Mythos in April 1975.

The building stands between Schloßstraße and Lepsiusstraße and has been vacant since 2013, so it can only be viewed from the street. Look up at the plastered facade for the "Humanitati" inscription beneath the roof. The bricked-up round windows on the first floor are best seen from the pavement opposite.

Below the roof, the inscription "Humanitati" (committed to humanity) is still legible, left from the years 1946 to 1957 when the Grand National Mother Lodge "Zu den drei Weltkugeln" was based here and reopened its "Ring der Ewigkeit" on 22 June 1946.