About 2 km southwest of Trzebiel, in the Lanka Valley, lies the “Teufelsstein” (Devil’s Boulder, or Diabelski Kamień in Polish). It is easily accessible via the partially paved “Juliusza slowackiego” Street and is located at the end of a 150 m long dirt road to the south of the street, on the edge of a small, forested area. Additionally, there is a small shelter with a high table in front of the Geotope.
Measuring 5.1 x 3.5 m wide and 2.5 m tall, it is the largest erratic boulder in the Muskau Arch. Its volume, including the underground portion of the boulder, is approx. 36 m3, which amounts to a total mass of 101 t.
The stone consists of medium to coarse crystalline (crystal size of 1-10 mm) alkali feldspar granite with a schistose texture. The mineral composition includes approx. 40% quartz, 40% microcline, 15% plagioclase and 5% biotite. Its chemical composition does not feature any peculiarities, for a granite, which is why it cannot be assigned to an area of origin. A large crystalline (up to 3 cm crystal size) pegmatitic granite has intruded into the main schistose granite.
Furthermore, the stone once held special significance as a place of worship. On its surface, three areas stand out where there are man-made openings and indentations, on the northwest, on the east and on the southwest sides. For example, there is a raised, circular shape with small, round depressions on the northwest side, where wooden sticks once might have been inserted, to represent the sun and its rays. In the early Middle Ages, large boulders were used as sacrificial alters by the immigrating Slavs.