49 huge limestone pits have been found in China's northwest. Experts believe, that they are the largest limestone formation in the world, writes the Daily Mail. Limestone pits are located at 33 and 32 degrees of the north latitude and occupy 600 sq / km. The largest limestone pit has a diameter of 520 m and a depth of 320 m. Scientists found these pits during excavations in the area of 5 thousand sq / km. They also found 50 pits with a diameter of 50-100 m and 50 natural caves.