Play structure, photographed at Earth Rebirth Day rally, Berkeley, California, Jan 1970. This rally was one of the many forerunners of the first international Earth Day on 22nd of April 1970. Photo currently digitized.
<a href="//commons.wikimedia.org/wiki/User:Foeniz" title="User:Foeniz">Hartmut Schmidt Heidelberg</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>