By Sierra Hartman

In the early ’90s, my friends and I used to tape flashlights to the handlebars of our bikes and go riding around in underground storm-drain tunnels. There was a whole network of these tunnels under the city that sat empty for most of the year. We would go for miles snaking up and down the sides of the tubes, clapping and yelling to see how far our echoes would carry, eventually popping out in some other part of the city covered in cobwebs and bat guano. When the tubes got too small, we laid down on skateboards and kept going. If we found a flooded part, we taped garbage bags around our legs and crossed our fingers.

The overwhelming feeling of adventure was intoxicating. I felt like one of the Goonies on my way to find One-Eyed Willy, albeit with fewer booby traps. My fascination with tromping around in underground tubes was also no doubt influenced in large part by my obsession with the Ninja Turtles. I mean, who didn’t fantasize about finding a long-forgotten subway station after watching Teenage Mutant Ninja Turtles II: The Secret of the Ooze for the first time? The idea that there was something literally deeper to explore beneath the white-bread suburbia we lived in utterly captivated my 12-year-old mind. Legos and pogs were cool and all, but this was real. We were seeing things that most other people had never even thought to look for. Without knowing it at the time, we had rolled our BMX bikes straight into the world of urban exploration.

The concept of urban exploration was first given a name in San Francisco in the late ’70s by a group called the Suicide Club. The club was known for all manner of shenanigans, including filling cable cars with naked riders, climbing the Golden Gate Bridge and throwing huge parties in the sewers. They dug into the guts of San Francisco and showed a select few people all the treasures that could be found. On at least one occasion, though, the word spread a bit too far. The History Channel’s Cities of the Underworld ran an episode on San Francisco in 2009, and the secret WWII bunker complex that was showcased experienced a growth spurt of popularity. The authorities eventually found the hidden entrance and sealed it up for good in 2011.

As much of a bummer as that was, there are still a great number of underground spaces to explore around San Francisco. The boom-and-bust mentality of this city has been an ongoing trend since the gold-rush days. So much of the city has been built in consecutive layers that traversing large parts of it entirely underground is not as difficult as you might think. Some of these places are relatively well trafficked by graffiti artists, but others have been so long forgotten that you could stand right next to the entrance and not realize there was anything there at all.

So why bother risking the demise of another underground San Francisco relic by publishing photos of it online? Because it’s good to pull back the curtain every once in a while and get a look at the city that came before us. Because that sense of adventure shouldn’t be relegated to childhood memories. And because, frankly, most people who are reading this will be content to look at the pictures and read the stories without going out to scramble around in dingy forgotten bunkers and smelly tunnels under the city. Most people just aren’t willing to risk trouble and discomfort for the payoff of discovery. I would ask one favor, though: If you happen to recognize any of these places, give yourself a pat on the back and keep it to yourself. We don’t need another hidden treasure being welded shut.

Squeezing between two slabs of rusty iron and concrete might cause you to reflect on the expiration date of your last tetanus shot.

One group of raccoons followed us from behind, while the other group kept pace about 50 feet in front. I couldn’t help but think they were up to no good.

Trying to figure out where you are based on what you can see through the openings in a manhole cover is like trying to put together a puzzle while looking through a straw.

There are few things more foreboding than a low roar at the end of a long tunnel.

Photographs by the author; design by Jessica Saia.