nature science history

Exploring the Secret Sidewalk in the San Francisco Bay Area

The old Spring Valley Aqueduct in the San Francisco Bay Area is a bemusing secret trail through nature for wayward travelers prefering the less beaten path.

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Fixtures from the “sidewalk’s” former use as an aqueduct can still be found along the path. Credit: Steve Rhodes

In the East Bay parklands of the San Francisco Bay Area near Fremont, California, there is a curious little trail known as the Secret Sidewalk. Well, it’s not really a sidewalk but rather the top of a strcuture that originally functioned as an aqueduct built by the Spring Valley Water Company about 100 years ago.

The half-buried concrete tunnel runs all the way from Calaveras Reservoir in the East Bay to San Francisco, at one point passing through the enchanting Sunol Water Temple.

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The Secret Sidewalk offers a hidden and scenic pathway through some of the Bay Area’s most undisturbed geography. Credit: Steve Rhodes

The intent behind building the aqueduct was to provide fresh water for the city. Irvington Pumping Station lifted the water to Crystal Springs Reservior via the Pulgas Water Temple, also on the peninsula.

However, the local water table dropped quickly, and the Spring Valley aqueduct ceased operation after only three years use.

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Walking along the path is not without dangers. Credit: Steve Rhodes

Today, Spring Valley Aqueduct isn’t good for much except as an amazing trail to hike along, walking through the open spaces of parkland on a readymade sidewalk of sorts. The surrounding area, which is otherwise untouched by civilization, is owned by the local government and walled off behind “no trespassing” signs.

Today, the Secret Sidewalk is also a gathering place for graffiti artists and teenage parties, who sneak into the area to enjoy the pleasant seclusion of a secret place only they know about.

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Open holes and grates allow a glimpse into the depths of the aqueduct otherwise hidden by the concrete “ceiling,” that is, the Secret Sidewalk itself. Credit: Steve Rhodes
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The Sunnol Water Temple, one of the many “water temples” throughout the Bay Area, is a major intersection of the aqueduct that forms the Secret Sidewalk. Credit: John ‘K’
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Brick foundry smoke stack. Credit: Steve Rhodes
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The Secret Sidewalk leading through a meadow. Credit: brettklynn
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The Secret Sidewalk from underneath. Credit: thedebbiecat
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Train tunned with the Secret Sidewalk passing above. Credit: brettklynn
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Remnants of the old brick factory along the sidewalk path. Credit: brettklynn
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The location of the Secret Sidewalk is, of course, secret but you can find the directions online if you search hard enough. However, in its current state the sidewalk is surrounded by “no trespassing” signs and dangerous to access. Credit: thedebbiecat

Sources: 1, 2, 3

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Written by Tamás Varga
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A sociologist and English major by degree, I've worked in the area of civil society & human rights and have been blogging in the fields of travel, nature & science for over 20 years.
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