Listener Britt McEachern is a tour guide in San Francisco, and spends a lot of time walking around city streets. He's noticed grids of glass embedded in the sidewalk and wants to know what they are. Take a journey with reporter Jessica Placzek to learn the purpose and origins of these gems beneath your feet.

Additional Reading:

What Are Those Grids of Glass in the Sidewalk — And Why Are They Purple?

Quiz: Test Your Bay Area Knowledge

Reported by Jessica Placzek. Bay Curious is made by Olivia Allen-Price, Jessica Placzek, Katie McMurran and Rob Speight. Additional support from Julie Caine, Paul Lancour, Kyana Moghadam, Suzie Racho, Ethan Lindsey and Patricia Yollin.