Null-space Tunnels under Yokosuka Navy Base
Deep within the solid rock of the Negishi Plateau in Yokohama, spreading beneath the old race-course Grandstand and Yokosuka Naval Base, lies a twisting warren of hidden World War 2-era caverns. Once filled with ancient munitions, bustling troops, and rooms full of military dossiers, they now rest in lonely silence, unexplored for up to 20 years, their secrets stopped up behind entrances back-filled with avalanche scree and trash, overgrown by thick vines in loamy earth, and walled off with sheets of blast-concrete.
I first heard about the Negishi Caverns from Brian in the comments section of my Negishi Grandstand Haikyo post. Brian was a ‘navy brat’ growing up on Yokosuka Housing Area atop the Negishi Plateau some 20 years ago, who with his friends explored the ruins of the area thoroughly, including the Grandstand. He told me the Grandstand was once barred to the public by only a slack barbed wire fence (now a plate metal fence 10 feet high) and comprised of a whole extra building- underneath which were access points to the warren of caverns.
Over a few weeks, Brian filled me in on his childhood adventures around the Negishi area, and I sat rapt as the emails came in. One story involved being attacked by a drugged-up homeless person in the Grandstand, who they fought off by blasting him with a fire extinguisher. In another they stumbled upon a cache of what might have been home-made terrorist rockets in one cavern ante-chamber. As they were leaving, an old guy who lived in a nearby shack attacked them in a berserk rage with a hoe, taking chunks out of tree roots as he swung at them. They escaped, just barely, but weeks later several rocket-propelled grenades were fired at the Air Base Telecommunications Tower, ineffectively as it happened, though Brian told me he remembered being woken up by three loud bangs one morning, and later seeing the shrapnel divots in the road outside of his friend’s house by the Tower. The attacks were claimed by a Red Army Leftist group who wanted the US presence out of Japan.
I’m very grateful to Brian for telling me these stories- I know how this kind of thing is valuable- I had my own childhood adventures and I wouldn’t want them to be mis-represented by anyone else. To us, they had great meaning, and I’m sure the same is true for Brian. I’m also grateful for the detailed and accurate Google Maps he sent me, with information on every tunnel entrance he could remember. At the soonest opportunity, I went to seek them out.
The first trip I took out to Negishi was only a recon mission- to see if there were any tunnel entrances still accessible. I didn’t intend to venture in far, if I found any. In fact- I was quite concerned about going deep into the tunnels. The night before I set off, I lay in bed thinking of awful scenarios that could happen in a hidden tunnel, most involving me getting lost and wandering aimlessly until I died alone in the dark. Still, I went- searching for 3 main access points.
Before I reached the first though, I found a suspiciously old-looking tunnel mouth at the top of the plateau cliff-face, now stopped up, underneath a car park which was clearly once a larger building. I tugged at some of the trash in this entrance, but it was firmly wedged in, so I moved on.
The first scheduled stop took me up a long flight of steps to an odd-shrine/home, searching around it, then back down to the 3 three or four homes at the bottom of the cliff face. I stealthed through their back-yards, quickly strafing the wall for any sign of a tunnel entrance, even going behind a transformer power-hub and squeezing between a 20 feet tall landslide fence and the rock face- but the whole cliff had been blast-concreted over, so any tunnel entrance was completely covered. I moved on.
The second scheduled stop began at a church on base and led down to the RPG shack, but I couldn’t get in since the whole area had been absorbed by the Housing Facility and fenced off. I may yet go back and try again, but at the moment have no more information.
The third scheduled stop proved fruitful though. At the base of the cliff, at the start of a flight of stairs cut windingly into the rock, Brian told me of a tunnel entrance engulfed with vines and vegetation that he and his friends found by accident when they saw the greenery fluttering from an inner wind. I arrived to find the whole cliff face blocked off by a tall landslide fence.
I climbed the fence, then squeezed along behind it, wedged between it and the rock face, walking 4 feet high on a long heap of land-slide detritus, rich loamy soil, tree branches, and trash. I was wearing shorts and sandals, and afterwards counted some 40 mosquito bites on my legs.
Nevertheless I pressed on, attacking the cliff-wall and heaped soil with gusto, digging into it with my bare hands. I got totally filthy with the very black muck, stinking of wet and green sap. I was in the mud up to my knees and just about to give up when my fingers hooked around the lip of what had to be a tunnel entrance. I dug around some more, and cleared a 10inch gap between the mud-trash and the tunnel roof.
I got out my flashlight and peered in. For as far as I could see, the tunnel was filled with trash and only about a 10-inch space was clear. Not wanting to get any more filthy, or dig through broken glass and other trash with my bare hands, or stung any more, I resolved to come back at a later time, better equipped.
For my second trip to the cavern site I brought a lot more gear: Humvee wellington boots, waterproof pants and jacket, gloves, a new large Maglite, a shovel, string and paper and pen to avoid getting lost, and lots of batteries, water, and energy bars. I went straight to the overgrown tunnel, no longer concerned about mosquitoes with the waterproof gear all zipped up, and tucked into digging around the tunnel entrance. I cleared a deep enough space to shimmy through, then shimmied through.
Inside the trash tapered off and I could stand, but ran almost immediately up against a dead-end. The tunnel was only some 10 meters long, ankle-deep in mucky water, and scattered about with trash- broken ceramics, shells, boots, a tyre, cans of oozing liquid tar, a doll, half a tennis racket.
I took some photos, some footage, sat for a while trying to decide what to do next, then exited. But I didn’t give up. Brian had described a longer tunnel that ended in a dam-like wall, behind which the tunnel was filled with clear drip-water. I wanted to find that tunnel. I took my shovel and clambered over the heaped land-slide earth and roots to the deepest point, and got ready to start digging.
Then I saw the second entrance. It was off to the side, in back of a nearby garden, but not filled with trash and much easier to access. I counted my lucky stars that I had seen it by chance, then hurried over and slid down. It was much wetter and muddier than the first tunnel, but also larger- it turned to the left just up ahead. I readied the Maglite and set off exploring.
After the left-turn there was an empty room to the right, with a lot of buckets in the corner. Past that was a stopped up exit to the left, and the water-tunnel with concrete slab-dam to the right. Another dead-end.
I shone the light out over the water, but could only make out that the tunnel turned to the right. I considered climbing the dam and wading out into the water, but it was as high as my chest- and it seemed quite a risk to take, knowing the water would be cold, I was on my own, and had no knowledge of how far the water continued. I resolved to come back with more gear.
The third time I returned with Su Young- the only person brave and foolhardy enough to join me. We brought a bucket and 3 pipes with us- to first drain the water before climbing over. A lot of detractors said it would never work, siphons would never drain the tunnel- but once they were in place, the water roared through them and the tunnel drained to knee-height in about 20 minutes.
I climbed over the dam, and Su Young followed. The water went into my Wellington boots, but no higher. Unfortunately, round the next corner was another dead-end. End of the road. No secret munitions stash for us, or room full of military dossiers. I began to wonder if this tunnel had ever been connected to the military. It didn’t link upwards to the base, it seemed if anything rather like a sento, or bath-house. The water from behind the dam had channels in stone on the ground to run in, channels which led around the one chamber with the buckets in, which could have functioned as seats to sit on while washing.
Brian since suggested another possible tunnel entrance- which I may at some point go take a look at. At the moment though- I’m all tunneled out.
Su Young with the pipes siphoning behind her.
Location – Negishi, Yokohama
Entry - Lots of digging through muck, climbing, siphoning, scrambling.
Highlights -Moment my fingers found the tunnel ceiling through muck, watching the siphon tear into the dammed water, Su Young just doing it all fearlessly.
RUINS / HAIKYO
You can see all MJG’s Ruins / Haikyo explorations here:
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