The lost city beneath the waves? Scientists stunned by submerged pyramid
The Yonaguni monument continues to spark debate over its origins, with some convinced it’s a sunken relic of an ancient civilization.

The ground beneath your feet hasn’t always been there – at least, not in the form you see it today. Thanks to the slow grind of tectonic plates, a single supercontinent known as Pangaea eventually broke apart. Over millennia, and with time doing its quiet work, what lay beneath us ended up as part of the Americas, Europe, Asia, Africa, Oceania or Antarctica. Science has long explained how the Earth shifts and reshapes itself, but even the most grounded scientists sometimes find themselves staring at the world’s mysteries and wondering: how can this be?
The mystery of Yonaguni
How is it, for example, that nature could so precisely shape a rock formation – carving out what looks like a staircase long before humans conceived of such a thing – all without our intervention? That question lies at the heart of one of the most enduring geological enigmas of our time: the Yonaguni monument, an underwater structure off the coast of Japan that has sparked decades of debate. Was it sculpted by nature’s whim – or built by human hands?
This striking formation lies beneath the sea, though some researchers believe it may once have stood above ground. Roughly the size of five football fields and as tall as an eight-story building, Yonaguni’s massive walls appear to have been chiselled. The surfaces are unnaturally flat, the levels stacked like platforms, with steps that seem to connect them. Did humans shape this monument? The jury is still out.
Among the first scientists to study the site was Masaaki Kimura, who concluded that it was in fact man-made. According to Kimura, it was built on what was once the lost continent of Lemuria – a vast landmass proposed in the 19th century by British zoologist Philip Lutley Sclater, believed by some to have sunk into the Indian Ocean.
Other researchers argue that Yonaguni’s precise forms are the result of natural erosion and tectonic activity. But the mystery endures. Spanish explorer Diego Cortijo, founder of Ruteon, has visited the site and shares his thoughts online: “The symmetry of the cut lines, the supposed paths and carved pools make the theory of a natural origin seem improbable to many.”
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