January 5, 1987 (Bingyin twelfth lunar month sixth days), found in Inner Mongolia, a giant crater.


Xilin Gol League, Inner Mongolia Duolun County and Zhenglan Banner "the annular water system" craters found in the territory, is the largest in the four craters found in China, the world's second-largest crater.
Xilin Gol Grassland in Inner Mongolia Autonomous Region, a very special "the annular water system", this formation in the topography of hundreds of millions of years ago, "extraterrestrial" left to the prairie craters. to
the Luan River and Lightning River formed annular water system "is located in the Xilin Gol League Duolun County and Zhenglanqi territory, and was the ancient city ruins are integrated in the Yuan Dynasty temporary States and the provisional capital of the Yuan. Reporters to interview dollars on both the ancient ruins, specifically to see the crater.
Zhenglan Banner Cultural Affairs Bureau, told reporters, Luan River and Lightning River yuan on the ancient city of the annular moat. This loop water system, "the inner diameter of 70 km, the outer ring of up to 150 kilometers in diameter, with the naked eye is difficult to see the whole picture.
said that the crater via satellite found. In 1986, the State Geology and Mineral Resources, Ministry of Geology Institute geologist Edward Ng, this had been based on the satellite photos provide clues to the Duolun County Zhenglanqi site visits confirmed that the structure of this ring water system "used to be a huge meteorite remains of explosions pit. According to geological experts inspected the crater formed between the Jurassic and Cretaceous, about 140 million years ago, is one of the four craters found in China.
Currently, the yuan on both sites have been listed as national key cultural relics protection units, and declared a World Cultural Heritage. Zhenglan Banner initial development of both sites on some tourism projects, and supporting the construction of the yuan on the museum, Kublai Khan's summer palace, and a number of tourist facilities, admiring the endless stream of visitors in recent years. Then "the annular water system" structure craters developed to increase one the "crater wonders" tourism project will attract more tourists come to visit.