"underwater city" I think this place is the land of mystery that is unable to find the answers that exist or not. Often used to retrieve a mysterious place that came with the myth it is to relate to the story to hide secrets that can not find an answer.
But "underwater city" somewhere may include places that sink into the ground caused by men or caused by natural disasters.
The city ground is a story well most cities built deep underground "River" The river is a large river that stretches through many countries. Some parts of the Mekong River, an international border is barrier Thai and Lao. Mekong River in this section with the legendary story deep underground cities. Event related to the magic of the phenomenon "rockets" on the night of the Buddhist lent, a red light will appear in the spout up from the Mekong River, up into the sky and disappeared. It is a story told through the serpent made fireballs, he is Buddhist altar.
Along the Mekong River stretches, especially early on, Nong Khai-bueng Kan. There are many stories of people across two sides of the border to the city ground, which is considered the city of Naga themselves. Especially "the rapids of the Baba House" which is located near the Temple of Agios hongsila WA ... Amphur Muang, bueng Kan Honghaeng's khongboriwen River, this temple is believed to be the deepest point of the river. Known as "the navel of the Mekong River." The villagers believed the Mekong at the navel was deep underground Palace of the serpent.
"The cave is just land" follows social district is another place in the mystery story of deep underground cities. This cave was discovered by villagers hunting Woods to find this cave by mistake. Inside the cave there are also niche channels and low road hole caused by erosion of the underground water-filled arc. Many thousands are concave portion of the channel can be used to push a hole connecting is unbelievable, which is similar to that told by the Serpent's path. The villagers believed that the cave is the path to the city of the serpent that can travel to the South across the river. Finally, there is the Nong Khai to Vientiane during the story that this is a cave the path his thudong from Laos using crossed under the Mekong River into Thailand. This route is also the precepts as well as the brave only visible path.
Because "city ground" in which each of the mystery. With charm and comes with the legendary reliability Visit each location it is important to respect and strictly in accordance with the regulations.