What are the Mysterious Brick Circles in San Francisco Intersections?

<p>Spend some time walking around San Francisco, and you'll probably notice the large, brick circles decorating the pavement at some intersections. What are they for?</p><p><br></p><p>Reported by Sarah Craig. Bay Curious is Olivia Allen-Price, Jessica Placzek, Paul Lancour, Suzie Racho and Julia McEvoy. Theme music by Pat Mesiti-Miller.</p><p><br></p><p>Ask us a question at BayCurious.org.</p><p><br></p><p>Follow Olivia Allen-Price on Twitter @oallenprice.</p>