Celestial Ladder Kingdom(梯仙国):
In Chinese, it is pronounced as: tī xiān guó，Written as:

Legends of people living at the center of the Earth exist across all times and cultures, with some even claiming to have visited this subterranean world. During the Tang Dynasty, there were stories of someone visiting a subterranean nation similar to where the Immortals reside, known as the Celestial Ladder Kingdom.
In the first year of Emperor Zhongzong of Tang’s reign, there was a wealthy peasant. He was digging a well behind his estate, and after two years and over a thousand feet, there was still no water. Yet, he persisted in digging deeper. After another month, the well diggers suddenly heard sounds of chickens crowing, dogs barking, and birds chirping underground. Digging a few feet further, they uncovered a stone cave and entered through its opening.
Initially, they saw nothing but the stone walls as they sidled along. The cave turned a corner, and suddenly, they were greeted by the light of the sun and the moon. They continued down the path, and at the end of the cave, there was a mountain which they descended, only to find themselves in another world. One side of the mountain was immeasurably high, and the valleys and peaks seemed like realms of the Immortals. The rocks in the mountains were of a bluish glazed hue, and palaces made of gold and silver filled every valley.
There were also large trees in the mountains, their trunks segmented like bamboo and leaves like those of banana plants, blooming with large purple flowers as big as plates. Numerous colorful butterflies, as large as fans, fluttered among the flowers, and birds of five colors, resembling immortal cranes, soared between the treetops. Each valley had a spring as clear as a mirror and a white spring, its water as white as milk.
Approaching one of the palaces, the worker decided to enter and inquire about the place. Looking up, he saw a plaque above the palace gate that read “Mount Tian Gui Palace” in silver letters. Just then, two individuals emerged from two rooms inside the gate, looking very surprised. They were over five feet tall, with youthful faces, red lips, white teeth, and hair and beards as black and glossy as silk. Their clothes were extremely soft, woven from white mist and green smoke, wearing golden crowns, yet barefooted.
The worker asked the door official about the “Celestial Ladder Kingdom,” and the official replied, “This is where those who have just become Immortals are sent to continue their cultivation for seven hundred thousand days before ascending to Heaven, reaching the Jade Capital where the thirty-two Celestial Emperors reside, or traveling to Penglai Immortal Isle, Kunlun Paradise, or the mountain where the goddesses live. Only then can they obtain an official position in the Celestial Realm, be granted a decree and an Official Seal, and freely fly across the Celestial Realm.”
The worker further asked, “If this is a kingdom of Immortals, why is it beneath our country?” The official explained, “This is just the upper Celestial Kingdom below your country; above your country, there is another Celestial Kingdom just like this one, also called the Celestial Ladder Kingdom, exactly the same.” After this explanation, the official ended the tour, guided the worker back up the mountain to the path they came by, and had him drink a few more sips of water from the white spring.
Upon exiting the cave, people told him that three to four generations had already passed. The worker tried to share his story of the well, but no one knew of it. He then searched for the original well site, only to find a large, collapsed pit where the well used to be.