The Schellenberger Eishöhle is the biggest ice cave of Germany. It is also the only ice cave in Germany, which is open for tourists. The ice inside has an approximate surface of 60,000 square meters and a depth of up to 30 meters. Ice caves are caves formed in rocks, which contain huge amounts of ice. This ice may be thousands of years old. Ice caves are generally located in areas where the average yearly temperature lies around 0°C. In Central Europe it is higher (around 8°C), such low temperatures are found at a heights of about 1,500 to 2,000m asl. The Schellenberger Eishöhle has a typical morphology, the cave is going down continually from the entrance. This works as a cold trap, as cold air flows in during winter, as it is colder than the warmer air in the cave. In summer the heavier cold air is not able to leave the cave again, it is trapped. This phenomena is used by supermarket fridges, which keep the content cool although their top lap is open. The water from the surrounding rocks is warmer, especially the meltwater during snow melt, but when it enters the cave with its cool air, it freezes. During the summer the temperature may rise above zero, and some of the ice may melt. But ice caves are so close at the zero degree border, that at least a remains of the ice lasts all year. Because of the change between melting and freezing, the shape of the ice changes from year to year. Some parts of the ice have some kind of year rings, similar to trees. Some figures of ice close to the entrance vanish completely during summer, but similar sculptures reappear in the next winter. Every spring 800 to 1,200 hours of work are necessary to rebuild the paths on the changes ice surface. It is rather difficult and strenuous to visit this cave. There is no nearby parking lot, with a few minutes stroll to the cave. This cave is located at 1,570m asl at the slopes of the Untersberg. From the German side of the mountain the cave is reached by a three hour ascent to the Toni-Lenz-Hütte and then to the cave entrance. The parking lot is located at the B305 between Marktschelleberg and the Austrian border. A little easier is the use of the Untersbergseilbahn, the cable car from the Austrian side of the mountan, and the descent of about 200m to the cave entrance. In both variations appropriate clothes, good sturdy walking shoes and and warm clothes for the cave are essential.