San Francisco is 49 square miles, but contains more than 1,000 miles of sewer mains, running under every block. Take a trip with Bay Curious reporter Carly Severn into the depths of the city, and discover an otherworldly cave that has reached legendary status with some urban explorers.<a href="https://www.youtube.com/watch?v=726sQLKGAjk">VIDEO: Take A Trip Into San Francisco's Sewer System</a><a href="https://ww2.kqed.org/news/2019/10/31/tunnels-under-san-francisco-inside-the-dark-dangerous-world-of-the-sewers">Web story: Tunnels Under San Francisco? Inside the Dark, Dangerous World of the Sewers</a> Reported by Carly Severn. Bay Curious is made by Olivia Allen-Price, Jessica Placzek, Suzie Racho and Rob Speight. Additional support from Julie Caine, Paul Lancour, Patricia Yollin, Vinnee Tong and Ethan Lindsey. Learn more about your ad choices. Visit <a href="https://megaphone.fm/adchoices">megaphone.fm/adchoices</a>

It's Our Birthday! Come Behind the Scenes

Bay Curious is a show about your questions – and the adventures you find when you go looking for the answers. Join host Olivia Allen-Price to explore all aspects of the San Francisco Bay Area – from the debate over "Frisco", to the dinosaurs that once roamed California, to the causes of homelessness. Whether you lived here your whole life, or just arrived, Bay Curious will deepen your understanding of this place you call home.