The Marina District under your feet was built on the wreckage of one world's fair to house another, and it nearly returned to the bay in an earthquake. The Marina District occupies land that was bay water and tidal marsh until the Panama-Pacific International Exposition of 1915 filled it with sand, rubble, and the debris of the 1906 earthquake — including the broken wood and plaster of the destroyed buildings. The fill was left in place after the fair, and the Marina was developed as a residential neighborhood in the 1920s, with the Spanish Colonial and Mediterranean Revival houses you see today.
On October 17, 1989, a magnitude 6.9 earthquake struck while the World Series was being played at Candlestick Park. The Marina was one of the neighborhoods that suffered worst: the loose fill and bay mud liquefied under the shaking, and several buildings collapsed. Gas lines broke and fires burned for two days while firefighters struggled with broken water mains.
The disaster was nationally televised because the earthquake hit during the broadcast setup for the Series. The Marina was rebuilt, the fill was improved, but the neighborhood still sits on ground that will liquify again in a major earthquake. The street grid, the view of the bay, and the human need to live in beautiful places won out over geology.