Taken as part of the Wikimedia Foundation Photo scavenger hunt at the San Francisco Exploratorium on 2015-01-21.
<a href="//commons.wikimedia.org/wiki/User:Joakinol" title="User:Joakinol">Joakinol</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>