The Spielplatz is a playground area with a sand pit on the Platz. It is located on the eastern side of the Volksbühne next to the Grüner Salon and in front of the southwestern block of the Nazi-Bauten which border it with a small strip of private green space. On its southern side, the Pavillon and the Telefonzelle are connected. He competes with the Trinkerpark for the favor of people who would pretend that they are just sitting on benches and actually just want to be in the fresh air.
After the Demolition of the Scheunenviertel, a large part of the newly created fallow land was filled in from 1914 by the Volksbühne building. The right open space was initially filled with a lawn.
In 1921 the area was used as a storage area for Siemens & Halske AG. Since the war was over for now, one had to rethink and for some time turned into means of transport. Therefore, they used the space to build the A.E.G. Schnellbahn that ran through Berlin until 1930.
From 1927 the area was covered with a wooden fence by Alfred Schrobsdorff, which could be an early form of art in public space (in its current form), at least that was what some believed.
Later, the area was fenced in parallel to the street and, in keeping with the spirit of the times, planted with small trees that assumed a military formation. Every tree stood for a fallen SA man.  At that time there was still a wall in front of the front yard of the Nazi-Bauten.
Its first documented use in today's form dates back to 1937, when the "Memorial to the Murdered People of the Movement in the City Center" was misused.
On April 16, 1952, the area was the scene of a Thälmann Convention, which came to unveil a plaque of their idol at the Karl-Liebknecht-Haus. Then it was remembered how likeable this spot of earth could be ti just hang out.
A stage was set up here during the X. Weltfestspiele der Jugend in 1973. The idea worked so well that it has since been used for annual folk festivals under the code name Fest der Linken.
After that, the playground was fenced in for a few years and was only used by the kindergarten housed in the Pappschachteln.
The playground was renovated in the 2000s. After that it was also repeatedly the venue for open-air productions of the Volksbühne. 
- A. Gröschner: Berliner Bürger*stuben. Palimpseste und Geschichten.
- https://www.berlin.de/kultur-und-tickets/tipps/kinder/archiv/3881625-3149853-maerchenauffuehrungen-an-der -volksbuehne.html