It is believed that these caves were carved artificially in a system of underground tunnels and pantries. It is said that professor Chi Pu Tei and his students found tombs with skeletons of 1.38 m (4 ft 6 in) in height buried inside them. The skeletons have had abnormally large heads and small, thin and fragile bodies. In addition to the skeletal remains, Professor Chi Pu Tei and his students found numerous other items.

It was also suggested by theorists that these skeletal remains could have belonged to an unknown species of a mountain gorilla, but Professor Chi Pu Tei did not agree. There were no short notes honoring the deceased on the tombs. But instead, the team found more than 700 stone discs (“Dropa Stones”) with 8 cm holes in diameter at their centers. Carvings of the rising sun, the moon, stars, the earth, mountains, and dotted lines linking the earth with the sky discovered on the walls of the caves.

The discs and the cave paintings said to date approximately 12,000 years. Their whereabouts remain a mystery even today. The alleged finding raised numerous questions. Who were these mysterious beings?

What were the enigmatic discs, and where did the star maps carved on the cave walls lead to? 12,000-year-old Dropa Stones.Each Dropa Disc, reportedly, would have inscribed with two thin grooves that spiral from the edge to the central hole. It believed that the mysterious 12,000-year-old Dropa Discs and other items found during the expedition kept at the Peking University for 20 years.

All the attempts to decipher the writings on the Dropa Discs went futile. However, the discs examined by Dr. Tsum Um Nui, in Beijing around 1958. Dr. Tsum Um Nui concluded that each groove consisted of a set of small hieroglyphs of unknown origin. The rows were extremely small that a magnifying glass was essential to see them vividly.

Many of the hieroglyphics worn out by erosion. When Dr. Tsum allegedly deciphered the symbols, he disclosed how the ancient writings tell a story of an Alien encounter. Where an ancient alien ship crash-landed on Earth some 12,000 years ago. According to Dr. Tsum Um Nui, one of the hieroglyphic lines read:

“The Dropas came down from the clouds in their aircraft. Our men, women, and children hid in the caves ten times before sunrise. When at last they understood the sign language of the Dropas. They realized that the newcomers had peaceful intentions.” Another section of the 12,000-year-old Dropa stones, reads about the regret of the inhabitants of the mountain (tribe of the Ham). Because the aliens had crashed their spaceship. And they could not build another to return to their planet.

The discovery of Dr. Tsum allegedly published in 1962. However, it is also said that he became a subject of mockery, and out of shame. He left China in exile moving to Japan, where he would later die. Many people convinced that the Beijing Pre-History Academy would never have allowed him to publish or discuss his find again. Furthermore, due to the fact that “Tsum Um Nui” is not a real Chinese name. Some critics suggest that the man never existed. Others claim that Tsum Um Nui a Japanese name adapted to the Chinese language. In addition to his theories about the 12,000-year-old Dropa Stones, there is no further evidence that he ever existed.

In 1974, an Austrian Engineer, Ernst Wegerer, was on a guided tour of the Bampo Museum in Xian (a city in China), where he saw the stone. He captured photographs of two discs that matched the descriptions of the Dropa Stones. The Austrian Engineer observed a hole in the center of each disk and hieroglyphs in grooves, partly crumbled, like a spiral.

When the manager asked about the discs, he could not tell anything. However, he permitted Ernst Wegerer to take one in his hand and photograph them. He asserts that in his photos the hieroglyphs cannot be seen as they have been hidden by the flash from the camera and have also deteriorated. By 1994, the discs and the manager had disappeared from the museum.

People have been skeptical about these 12,000-year-old Dropa Stones. Critics rejected the story of the Dropa discs, arguing that it was a mixture of deception and urban legend. Writer David Richie mentions that these stories intrigued Gordon Creighton, a member of the Royal Society of Anthropology and the Royal Society of Geography.

In the investigation, Creighton considered the allegations about the Dropa unfounded and detailed his findings in an article for the Flying Saucer Review. It is difficult to discover credible evidence to show that the Dropa Stones exist or have existed in the past.