Some had a practical reason for venturing underground—quarrying stone for building material, digging out cisterns or mining salt. Others were drawn there for spiritual purposes, building shrines ...

Cisterns are large water storage tanks similar to rain barrels. Like rain barrels, they are designed to collect rainwater from your rooftop and store it for later use. Unlike a standard rain ...

It's been a constant reminder. In the last several years, San Francisco has added underground cisterns for a citywide total of 222, many holding up to 75,000 gallons of water. The largest is ...