Boybuloq Cave
The cave is the deepest known cave in Asia having been explored to a depth of from the entrance. At the lowest discovered level a water-filled siphon blocks further exploration. It is thought that the cave has the potential to be the deepest known cave in the world, with a theorised depth of making it deeper than the Veryovkina Cave. The explored length of the cave is .
Harz
Geomorphological processes have led to the formation of caves in the gypsum, dolomite and limestone layers of the Harz. These dripstone caves include Baumann's Cave, the Unicorn Cave, Hermann's Cave, the Iberg Dripstone Cave and, on the southern edge of the Harz, the Heimkehle.
Because the older formations contained many mineral deposits, they were explored very early on by the mining industry. The mines have often been turned into show mines. For example, the Samson Pit was for a long time the deepest mine in the world. Other show mines are the "Büchenberg", "Drei Kronen & Ehrt", the "Röhrigschacht" show mine, the "Lange Wand" show mine in Ilfeld and the "Rabensteiner Stollen" show mine in Netzkater.
Others have been turned into mining museums, like the Upper Harz Mining Museum in Clausthal-Zellerfeld, the Lautenthal Mining Museum with its pit railway or the Rammelsberg Mining Museum near Goslar, which is a UNESCO world heritage site. The Roter Bär Pit in St. Andreasberg also served as a training mine until the 20th century and is today, preserved true to the original, as a visitor mine.