In the Urumqi region of the northwestern edge of the Junggar Basin in Xinjiang, there is a "castle" known as the "Devil City". It is like a natural labyrinth, rising up in the wilderness with no landmarks to reference. The internal topography is extremely bizarre, with mounds of earth arranged into a huge maze, making it difficult to orient oneself. Even if they are just a few meters apart, people often can only hear voices but not see the people themselves. Within a radius of more than 10 square kilometers, crisscrossing dry valleys resemble "streets" in urban areas, while variously shaped rock terraces on both sides of the dry valleys are randomly combined into two or three layers, each about 20 to 30 meters high, and some even higher. They resemble pavilions, towers, sacrificial altars, and pagodas, like a deserted and abandoned city. When the wind blows, it stirs up layers of yellow sand, making the sky and earth dark. The violent desert wind howls through it, emitting terrifying screams like ghosts and wolves, sometimes like thousands of wild beasts roaring, and sometimes like the groans of the dying, which is truly chilling. After night falls, the castle is shrouded in a layer of cold moonlight, and the scene truly resembles a mysterious ghost city.
It wasn't until 1900 that the Swedish explorer and geographer Sven Hedin conducted an investigation there, and the truth of the "Devil City" was finally revealed to the world. It turned out that more than 100 million years ago, this place was once a huge freshwater lake with a humid climate and beautiful scenery, just like the water towns of southern China today. However, with the rapid uplift of the Tibetan Plateau, high mountains blocked the southwest air currents and cut off the water vapor from the Indian Ocean. Over the years, the climate became increasingly dry, and with the earth beginning to rise (the local altitude is now 300-500 meters), the lake gradually turned into a vast Gobi plateau. However, the exposed rock layers are mostly soft mudstone and harder fine-grained rocks, which are sedimentary rocks formed by the interaction of soft mudstone and harder fine-grained rocks. Over the years, with the continuous changes in climate, the rocks have been constantly eroded by rainstorms, sun exposure, and strong winds. Especially in the strong northwest wind carrying sand and gravel, the soft rock layers eroded faster, and the harder parts that remained on the surface were shaped into bizarre forms, thus creating the "Devil City".
The "Devil City" in Urumqi belongs to a typical Yadan landform, a masterpiece of wind and water erosion. In addition to Urumqi, there are also Bailongdui and Sandlongsha in Xinjiang. These three places are world-famous representatives of Yadan landforms and are collectively known as "the three most beautiful Yadan landforms in China". In addition, there is Dunhuang Ancient Sea Yadan in Xinjiang, which is a group of medium- and large-scale Yadan landforms with colorful shapes and high density, which is rare in the world.