Design

The Sublime Cisterns of San Francisco

Subterranean vats were an emergency response to the city being repeatedly and savagely burned to the ground.
A worker stands inside a cistern in San Francisco's Mission District.Robin Scheswohl/San Francisco Public Utilities Commission

Traipse around San Francisco long enough and you’ll notice weird patterns on the streets: bricks arranged in sprawling circles and rectangles, reminiscent of ancient stoneworks or satellite calibration symbols.

But it’s what lies beneath these curious road-tattoos that’s really interesting. Embedded in the earth are colossal cisterns that hold sometimes substantial artificial lakes. Are these lightless pools meant for the swimming pleasure of C.H.U.D.s? In reality, they’re a physical reminder that San Francisco historically has been a tinderbox, and it’s always good to have extra water lying around in case of a nasty fire.