Mysterious Brick Circles

San Francisco has mysterious brick circles implanted in certain street intersections. They look strange and random. They are found all over the city. The first one can go without mention, but once you see a second, a third, a fourth... it's enough to make the most apathetic people curious.

It turns out that these mysterious brick circles are an important part of San Francisco history. After the 1906 earthquake and fire that destroyed the city, the government created an emergency water system to prevent future disasters. The circles in the pavement mark the location of huge underground cisterns, each containing thousands of gallons of pressurized water.

More: What firefighter's spokesperson has to say

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