Yoichi R. Okamoto had been LBJ's official White House photographer, but in the summer of 1973, it looks like he was shooting for DOCUMERICA, a massive EPA photo study project designed to assess the state of the environment, to ferret out best practices for urban living, etc. At least that's what I imagine it said on the expense report for what otherwise looks like a sweet boondoggle of a trip to Vienna.
I love that Okamoto's official caption emphasizes that this temporary astroturf playground in the plaza of the Rathaus, as "BUILT ABOVE AN UNDERGROUND PARKING LOT."
When obviously, the most important thing--besides getting that kid about to get brained on the see-saw to a doktor, that is--is the scattering of giant playballs by the fort.
Seriously, where'd these things come from? They're awesome. They look like you could roll a kid down a hill in one. They are exactly the kind of giant, rotation-molded polyethylene plastic plaything that the 1973 oil embargo would drive to extinction in a few months. Any leads on the designer or manufacturer, or on any other Spielplatz sightings, pre- or post-OPEC, are welcome.