Mysterious 'Underwater City Walls' Emerge Off Vietnam's Quy Nhon Coast

Mysterious underwater rock formations, stretching approximately 4.5 km and locally known as 'Bờ Đập' (dike), have been discovered off the coast of Quy Nhon City in Vietnam's central Binh Dinh province. These formations emerge from the sea during low tides, particularly between the 15th and 18th days of the lunar month, off the coast of Nhơn Hải fishing village. One section of these rock formations, extending from Nhơn Hải to Hòn Khô Island, is about 1.5 km long. While submerged during high tide, its highest points rise to about 10 meters above the seabed and reach a width of 30-60 meters when exposed by the receding tide. Another formation, called 'Rạn Cầu', located about 1 km away in the Hải Giang area, spans approximately 3 km with a width of 3-4 meters. In 2024, the Gia Lai Museum, in collaboration with the Vietnam Institute of Archaeology and local authorities, conducted field surveys of these rock formations. Preliminary findings suggest that these structures were primarily formed through the long-term deposition of sediments in a marine environment over various periods. Layers of sand, marine organisms' remains, and sediment gradually accumulated to create their current structure. Natural transverse cuts are visible on the rock surfaces, and the two ends of the formations feature wide openings of about 50 meters, which local fishermen use for boat access. Analysis of mollusk samples from the surface sediment layers indicates that the area was accreted between approximately 1,000 BC and 700 AD. Based on this data, the research team hypothesizes that residents of the Sa Huynh or Champa cultures might have utilized these natural rock formations as mooring sites and shelters for their vessels against storms. However, Mr. Bùi Tĩnh, Director of the Gia Lai Museum, emphasizes that to definitively determine whether these rock formations are artificial structures, further archaeological excavations, geological and material studies, and dating are required to ascertain their function and purpose. Currently, there is insufficient scientific evidence to classify them as archaeological relics or purely natural geological phenomena. The museum plans to continue collaborating with the Vietnam Institute of Archaeology and the Centre for the Study of Ancient Capitals for more in-depth investigations. These 'underwater city walls' have become a unique attraction, drawing numerous tourists who take advantage of the low tides to paddle SUPs or row coracles to the rock formations for photography and coral viewing.