Where there is something strange and secluded, the strange and secluded will gather. In no other place does that hold true like abandoned-yet-safe former public works structures.

In the East Bay parklands of the San Francisco Bay Area, one such magnet for the curious and the mischievous is a trail enchantingly known as the Secret Sidewalk.

Not a sidewalk at all but rather the top of the Spring Valley Aqueduct—a half-buried concrete tunnel running all the way from Calaveras Reservoir in the East Bay to San Francisco—the aqueduct ran through the similarly enchanting Sunol Water Temple. The intent 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. Alas the local water table dropped precipitously, prompting formation of Alameda County Water District. Spring Valley aqueduct ceased operation after only three years use. Then Hetch Hetchy aqueduct began delivery from the Yosemite area, gravity fed spanning 200 miles. Initially Hetch Hetchy water was backfed into percolation ponds surrounding Niles to recharge depleted local aquifers.

Today, Spring Valley Aqueduct isn’t good for much except as a bemusing trail to visit and hike along, walking through the open spaces of parkland on a readymade sidewalk of sorts. The surrounding area is otherwise untouched by civilization, owned by the local government and walled off behind “no trespassing” signs. This leads to the aforementioned utility of the Secret Sidewalk as a gathering place for graffiti artists and teenage parties, able to sneak in and enjoy the pleasant seclusion of a secret place only they know about.

Bay Area officials have considered repurposing the aqueduct or even putting it back into use as a solution to the growing mischief surrounding the area, but thus far no plans have been carried out.

In the meantime, the Secret Sidewalk’s legend will likely continue to grow, passed along by word of mouth from person to curious person. As a meeting ground. As a secluded lover’s lane. As a safe and quiet place to be where you’re not supposed to be. It’s only appropriate – after all, the aqueduct’s original purpose was to deliver water to places it wasn’t meant to be. Now it delivers urban explorers and legends in the same way.

Update May 2020: In 2018, the property owners announced plans to demolish the Secret Sidewalk, but as of May 2020 it still stands. In its current state, the sidewalk is surrounded by “no trespassing” signs and dangerous to access.