Hi Dennis. I saw a Japanese documentary about the city. Here is link you may want to look at. There isn’t very much that I can add to it.

You land on a ledge overlooking a deep ravine. Water runs swiftly by. Following your divemaster, you launch off the precipice and float weightlessly across the 21m deep ravine. This chasm may be as wide as 64m. The current here is at its strongest; those who do not bring cameras have no regrets. Gliding across the ravine, are numerous parrotfish, large emperor angelfish, and schools of blue anthis, their bright yellow tails acting as guides across the stone steps on the wall opposite your launch point.

Landings on these steps reminds you of a fighter plane being arrested on the deck of an aircraft carrier. Search for a handhold to drop the hook (or hand) on. Once hooked, the momentum swings you around once again. This visual perspective creates a deep respect for the magnificence of this gorge of limestone and sandstone shaped centuries before the birth of Christ.

The gorge is filled with tropical fish flying by or cruising into the current, criss-crossing your field of vision. It is reminiscent of a scene out of a Star Wars epic. Streams of bubbles move horizontally instead of upward. The current feels even stronger than that of Palau's Blue Corner. But the deep and translucent blue is inspirational.

The real story behind The Monuments is in its theories in how it was formed. Graham Hancock, author of Heaven's Mirror, included the Yonaguni Monuments as an unexplained phenomenon, and seeks to explain via astronomy how they may fit into ancient navigational aides that may have had significance to an ancient culture in the Pacific the predates recorded history.

The strongest, and most factual theoretical approach, I feel, comes from Professor Masaaki Kimura, a research geologist from the University of the Ryukyus in Naha City, Okinawa, who is working closely with Aratake-san. He has published several technical papers concerning the age and origin of these monuments. He reports that they appear to be between 8,000 to 10,000 years old.

Prof Kimura theorises that the monuments are now underwater because of the infiltration of the oceans since the end of the last Ice Age, which coincides, with the purported age of these monuments. Fellow geologists concur that his theory is supported by facts that indicate the end of the Ice Age some 10,000 years ago. The subsequent rise in the world's oceans supports his theory that infiltrating water has covered these Monuments to a depth of 33.5m.

Prof Kimura points out that a rock wall surrounding the most prominent areas around the monuments has a gate in it. A perfectly laid lintel rock and square passageway opening in the wall that would be a gate. This is typical of any monument or holy place in an ancient Asian culture.

It's also possible that the monuments were manmade, and that it was a quarry where stone was removed for construction at another site. There is no evidence of any slag rock at the bottom of the monuments that could possibly support the theory that it is a natural phenomenon. If nature did it, then where did all the rock fall to?

The steps, moving up in a pyramid shape, remind one of a quarry. Aratake-san (the discoverer) points out that in many places, notches are cut in symmetrical shapes, and aligned in perfectly straight lines in the same way a stonemason would line up to cut rock. The alignment of notches are observed throughout the rock structure. Even more supporting facts are constantly being discovered and documented.

• Sunkin City