This mysterious tunnel in Japan is like none you’ve ever seen before

A road that isn’t wide enough for cars and a dark, secret chamber are just some of the surprises at this off-the-beaten path destination.

What do you think of when you hear the word tunnel? Do you imagine a shiny, wide tunnel on a freeway? Or a busy tunnel on a suburban highway?

Today we would like to introduce you to a tunnel in Japan that’s neither of these. In fact, it’s one of the most unusual tunnels you’ll find in all of Japan, and it’s located off the beaten path in the tranquil tea-farming city of Kakegawa in Shizuoka Prefecture.

This tunnel is still a bit of a secret to even Japanese people outside the city, and it’s said to be one of the narrowest in the country, so our intrepid reporter Haruka Takagi left her car at home and hopped on her bike to explore the deep, dark secrets of the cave-like thoroughfare.

▼ Heading towards the mountains, but still not far from a main residential area, Haruka took a narrow path that can only be accessed by light vehicles.

The road here is so narrow that car drivers will no doubt become skeptical of their ability to drive any further and would do well to back up and return by foot or bicycle. Luckily, Haruka’s bike was ideal for the terrain, and after travelling about 200 metres (0.12 miles), the trees overhead became dense, the air around her cooled and she could see the tunnel zooming up towards her.

Rather than stop to explore, she decided to zoom right through the cylindrical opening, and she suddenly felt claustrophobic as the walls curved themselves around her.

Even more surprising was the steepness of the road inside the tunnel, and as she revved the bike to give her some extra speed, she ducked as the smooth walls gave way to a dangerously low rocky ceiling.

It was a hair-raising experience, and Haruka felt a sense of relief flood over her as she approached the light at the end of the tunnel. Once she’d made it through to the other side, she stopped the bike and felt weak at the knees after the surprisingly nerve-wracking ride.

She had no idea where the path ahead of her led, and there wasn’t any sign of life to be seen. It was as if she’d travelled through a portal to another world, and that portal was one of the weirdest and narrowest she could’ve imagined.

She hopped off her bike and decided to investigate the tunnel, which goes by the name Iwayazuido (“Rocky Valley Tunnel“). The side she exited from looked like something from a fantasy world, with roots and moss growing wild around the opening, making it seem more like a cave than a tunnel.

Stepping into the darkness, Haruka could see the more rounded opening at the other side where she’d entered, and she found that the tunnel was more vertically elongated, with a relatively high ceiling height.

▼ The sign outside the tunnel puts the height at 170 centimetres (5.58 feet).

The rocks at this end had been marked by tools, likely from the workers who’d built it, and Haruka could make out some writing on the walls, including “石”, the kanji for “rock”.

▼ Here in the quiet darkness, the markings looked more like staring, open-mouthed faces carved by an ancient tribe.

Mustering her courage, and turning on her flashlight, Haruka ventured further into the tunnel. With the sound of her footsteps echoing as she walked, a warm, dusty wind blew through the passageway and her smartphone lost its connection, reminding her that she was underground, with a mountain of trees above her.

▼ That’s when she discovered there was a side chamber inside the tunnel.

While a lot of tunnels have small, carved-out areas on their sides as a safety precaution for people to step into to avoid traffic, this side chamber was surprisingly large, stretching about a metre away from the tunnel.

What’s more, the walls had been fitted with hooks, from which lanterns could be hung. These seemed to be original fittings, likely created by workers, although she wasn’t sure why the chamber itself had been carved out.

The sign, which reads “bottles (or else colour)” was a bit of a mystery as well. This type of sign is usually used at recycling points where brown beer bottles and other coloured glass is to be put out separately from clear glass, and seeing as there were no other related signs here, which would be the case if it had been used as a recycling area, Haruka figured someone may have left the sign here as a prank.

Prank or not, the sign lended an eerie, lost-civilisation feel to the pitch-black room, and Haruka decided to snap a photo of herself here, setting up the flash and timer on her camera.

However…

Every time she tried to take the photo, the flash refused to work, resulting in a pitch-black photo.

▼ The red light is from her video camera, which was recording at the same time.

No matter how many times she tried to take a photo of herself, the flash refused to work. While Haruka isn’t one to believe in ghosts and spirits, she couldn’t help but feel she wasn’t alone in this cavern, and the camera glitch began to rattle her, so she headed back out to the tunnel and swiftly made her way towards the light at the other side.

▼ The central portion of the passage was incredibly rocky so she made sure to watch her head as she walked through.

▼ Some of the larger, more protrusive rocks were marked with fluorescent paint to prevent people from hitting them.

As she made her way to the end where she’d entered on her bike, she came across a particularly large chunk of rock jutting out of the ceiling. It appeared to show traces of workers’ efforts to remove it during construction.

▼ The rocks here protrude to the point where they might hit your head.

While the side she’d exited from was beautifully misshapen and covered in moss and roots, this side of the tunnel looked very different, with a tubular entrance that resembled a metal pipe.

▼ Haruka had never seen a tunnel with such a strange shape before.

▼ Here at the entrance, Haruka was more successful in setting up and capturing her shot.

After exploring the tunnel, Haruka felt like she had more unanswered questions than before she’d entered, so she phoned up the Tourism Exchange Division at Kakegawa City Hall to find out more about the mysterious site. They weren’t able to answer her queries straight away, so they contacted Kakegawa City Central Library on her behalf and sent her a document called “Asuka Local History” (Asuka refers to the Asuka district of Kakegawa City, where the tunnel is located).

According to the document, excavation work on the tunnel took place around 1884. The west exit (where Haruka exited on her bike) had a soft sandy geology, but the east exit (where she’d entered on her bike) was more difficult to construct, as it hit rock at the three-metre point.

As a result of being surrounded by rocks on the upper left and right, the construction team dug downward, creating the steep incline from east to west. The more modern, tubular entrance at the east exit was added in 1970.

As for the mysterious chamber inside the tunnel?

▼ The document says this was a hole made as initial work on constructing a well.

As far as Haruka could tell, there wasn’t anything here that looked like a well, but it’s long been said in Japan that “spirits collect around water.” This detail sent shivers down Haruka’s spine as she realised this may have been the reason why her camera flash suddenly stopped working in this area.

The tunnel is such a mysterious site that even the Tourism Exchange Division at City Hall wasn’t clear on its history, so Haruka was glad to be able to learn more about the details of the site from local documents. If you’re planning a visit, Haruka recommends going by foot, bicycle or motorbike, as there’s no way a light vehicle will be able to make it through the narrow tunnel.

▼ And if you go by bike, don’t forget to duck to avoid that rocky ceiling.

Given the history of old roads, and structural safety concerns due to ageing, there’s no telling how long dug-out tunnels like these will be around for. As one of the narrowest and most unique tunnels in Japan, this 137-year-old structure has stood the test of time, shuttling locals from one side of a mountain to the other with ease, and here’s hoping it’s still here in another 137 years’ time as well!

Site information
Iwayazuidou / 岩谷隧道
Address: Shizuoka-ken, Kakegawa-shi, Kamisaigo 981-1
静岡県掛川市上西郷981-1

Photos: ©SoraNews24
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