17:38 30-11-2025

Japan's hidden enigmas: Yonaguni site and Iya vine bridges

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Explore Japan’s lesser-known wonders: the debated underwater site off Yonaguni Island and the hand-woven vine bridges of Shikoku’s Iya Valley, mystery endures.

Sumo, sushi and sakura aren’t the only symbols of Japan.

Beyond the glossy postcards with familiar scenes, there are places that rarely make it into travel brochures. One lies beneath the waves off tiny Yonaguni Island; another sways high over a mountain gorge in the heart of Shikoku. Each puzzles researchers in its own way and leaves questions without tidy answers.

What did they find under the water off Yonaguni?

Yonaguni, a small island at Japan’s western edge, sits closer to Taiwan than to Tokyo, yet it became known not for geography, but for what rests on the seafloor nearby.

In 1986, a diving instructor noticed massive ledges, platforms and crisp right angles underwater. Some sections looked as if they’d been shaped by human hands, sparking a debate that hasn’t really faded.

One camp argues the site could be the remains of an ancient structure—perhaps even a city—thousands of years old. Supporters say they can pick out stairways, pathways and columns among the blocks.

Most specialists, however, lean toward a natural origin. In this area, formations like these can occur on their own, driven by the local rock and tectonic activity.

There have been no official excavations, and Japanese authorities have not designated the site as a historic monument. Even so, Yonaguni keeps drawing divers from around the world who want to see the enigma with their own eyes. It’s hard to deny that uncertainty only adds to the pull.

Up in the mountains, bridges woven from living vines

In central Shikoku, tucked into the slopes of the Iya Valley, another unusual tradition endures: suspension bridges braided from wild vines.

The most famous, Iya Kazurabashi, stretches about 45 meters and hangs roughly 14 meters above a fast river, weighing close to five tons. Once, these crossings gave locals a way to escape enemies quickly—the vines could be cut when needed.

Today the bridge is renewed every three years, preserving the methods of earlier generations. Travelers still inch across, gripping the weave and watching their footing on the planks as the river roars below and the span shifts with every step. The experience feels both precarious and deliberate—part challenge, part ritual.

Despite its reputation, Kazurabashi remains rooted in local traditions, and other, less publicized bridges nearby are no less striking.

Different, yet alike

The Yonaguni formation and the Iya vine bridges may seem unrelated, but they share one thing: they sit far from standard routes. You won’t find them on most package itineraries, and that very seclusion makes them stand out.

Both carry a sense of mystery: it’s unclear who might have shaped the stone-like forms underwater, and it remains a puzzle why, in a modern age, people still hand-weave bridges from vines. Perhaps the appeal lies in that tension—between what nature makes and what people choose to preserve.

The inexplicable draws us in

The Yonaguni site continues to fuel debate among experts, keeping the intrigue alive. The vine bridges, for their part, show that ancient practices can endure in the 21st century without modern materials. Maybe that persistence is exactly what makes these places impossible to forget.