Ancient Underwater Wall of Nhon Hai in Quy Nhơn Đông, Vietnam

All Vietnam Quy Nhơn Đông Ancient Underwater Wall of Nhon Hai A mysterious submerged wall stretches from the coast of Nhon Hai toward Hon Kho Island, emerging from the sea only twice a month. The submerged wall becomes visible during exceptionally low tides along the coast of Nhon Hai, Quy Nhon. lancaster / Atlas Obscura User The submerged wall becomes visible during exceptionally low tides along the coast of Nhon Hai, Quy Nhon. lancaster / Atlas Obscura User At the coast of Nhon Hai in Quy Nhon, a mysterious wall lies partly submerged beneath the sea. The structure extends from the rocky coast of Hai Nam toward Hon Kho Island and becomes visible only when the tide recedes deeply.

Local fishermen have long known about the structure, while its exact age and purpose remain unknown. The wall has a remarkably flat surface, reportedly more than 10 meters wide in some sections. Local divers have described it as being made not from individually laid stones or bricks, but from a dense, solid material resembling mortar.

Some theories suggest it may have served a defensive or coastal-protection purpose, and it is sometimes associated with the ancient Champa landscape of the region, but no archaeological evidence has yet confirmed its origin or date. For a few days around the lowest tides of the lunar month, sections of the submerged structure can emerge above the water, creating the unusual sight of what appears to be an ancient wall crossing the sea. Its uncertain history, changing visibility with the tides, and location between the mainland and Hon Kho Island make it one of the more enigmatic coastal features around Quy Nhon.

Get more unusual and extraordinary places each week with the Atlas Obscura Places newsletter. Your newsletter subscriptions with us are subject to Atlas Obscura's Privacy Policy and Terms of Use. The wall is best observed during exceptionally low tides, when sections of the structure emerge from the water.

Local accounts indicate that the lowest tides often occur around the first and middle of the lunar month, although visitors should check local tide conditions before attempting to reach it. The structure is located in shallow coastal waters, and access should be arranged with local boat operators rather than attempting to walk or swim to it without local guidance. Its origin and construction date remain unconfirmed.

Visitors should treat it as an archaeological mystery rather than assuming that it is definitively a Champa or ancient defensive structure. Hidden behind a Target are pillows of cooled lava that formed at the bottom of a deep lake in the Mesozoic Era. A strange rock formation with numerous legends trying to explain it.