Many of the cisterns existed back in 1906. Wherever you see a circle of red bricks in an intersection/street, there's a cistern. Problem was the fire chief was

Many of the cisterns existed back in 1906. Wherever you see a circle of red bricks in an intersection/street, there's a cistern. Problem was the fire chief was killed in the quake and he was apparently the only guy who knew where all the cisterns were.