Bold claim: Tokyo’s subway hides a secret floor, and it’s not for the public to use. But here’s how the mystery actually unfolds...
There’s a single level inside an underground maze that only staff can access, not everyday riders. A reader recently asked our Japanese team for help:
“There’s something bothering me on my commute. Could you look into it?”
The tip pointed to Korakuen Station in Tokyo, on the route from the Marunouchi Line to the Namboku Line. There, an elevator button is labeled for a floor called “B3.” But given how the station platforms are arranged, that floor seems out of place, and the reader felt hesitant to press the button. So our reporters headed to Korakuen Station to investigate the so-called mystery floor.
Upon arrival, we walked along the Marunouchi Line platform and spotted a mural on the wall that looked like a Dragon Quest castle. The artwork felt fitting for our quest, yet it also suggested that challenges—and perhaps danger—might lie ahead.
Tokyo’s train stations are famously vast, often described as dungeons. The mural seemed to invite us to push forward, defeat the boss of the station, and rescue the princess, so to speak.
We checked the signboard and headed for the elevator. It looked like a standard lift at first glance.
The Marunouchi Line operates on two above-ground levels, while the Namboku Line runs across six underground levels. The height difference between them is about 41 metres (134 feet), making these two lines among Tokyo’s largest in terms of vertical separation.
Step inside the elevator on the B1 level, and you’ll see a control panel with B1 labeled 改札階 (the Ticket Gate Floor), B5 labeled 都営線連絡階 (Toei Subway Connecting Floor), and B6 labeled ホーム階 (Platform Floor). This matches the floor list posted outside the lift. Yet inside, there’s an extra, unlisted floor: B3, with no explanation next to it.
Bravely, we pressed the B3 button. It didn’t light up, and an unexpected calm voice announced, “There’s no stopping on that floor.” The brief pause in the elevator ride made everyone in the car turn to look, wondering why we touched a floor that everyone else ignores. But the moment passed as the elevator continued downward.
We prepared our camera to document the mystery floor and captured a video of what we saw on B3. The door opened to a space that appeared operational but not intended for public access. It was bright, but there were no people—more like a setting in a zombie game where danger could arise at any moment.
What explains B3? A closer look at the doorway sign reveals the purpose. The label reads 設備変電設備 (Electrical Substation Equipment). In other words, B3 is a floor dedicated to equipment that powers the underground station’s operations: the subway trains, the lights, the escalators, and the entire subterranean ecosystem that keeps the system running. Substations convert high-voltage electricity from the power company into usable levels for trains and station facilities. While the general public can’t access B3, maintenance workers do, likely with special keys, codes, or prior staff authorization, which explains why the button exists in the elevator yet remains off-limits to riders.
In short, B3 isn’t a hidden hangout or a secret showroom; it’s essential infrastructure hidden in plain sight—an engineering backbone that keeps Tokyo’s vast underground network alive.
Photos ©SoraNews24
Want to stay updated on SoraNews24’s latest stories? Follow us on Facebook and Twitter for fresh content as it publishes.
[ Read in Japanese ]
