Dyleň (Tillenberg, 940 m) is the most western Czech mountain and the one of the highest peaks of Český les (Bohemian Forest) Mts. Because of its location close to the western border it hasn’t been available for the public. In the sixties of the last century the military, radio and radar station was built on the top. In the 1992 the soldiers left, but already two years later the peak area with a concrete tower gained a private owner and has become inaccessible again.
Dyleň massif is geologically very interesting since in the direction from north to south there is a gradual transition from phyllites over mica schists (part of the Saxothuringian) to the paragneisses and migmatites (part of the Moldanubian Zone). The increasing degree of metamorphism is manifested by characteristic rock-forming minerals - biotite appears first, then garnet with staurolite, later andalusite, subsequently disappear chlorite, sillimanite occurs at the expense of muscovite, and finally cordierite occurs in association with potassium feldspar. Samples of banded paragneisses can be studied on the dumps of the abandoned Dyleň uranium mine.
Some of these minerals can rarely form large crystals - in the rocks on the Dyleň slopes red grains of garnet, staurolite black columns, and especially up to 20 cm long, pinkish andalusite crystals (often converted into fine grained mica) can be found. According to the legends, garnets were mined by the Venetians, and verified reports refer to the gold extraction on the western slope of Dyleň in 1792. Even nowadays small gold nuggets can be paned in sandy streams.
The visitors are mainly attracted by small and picturesque rocks, which are the result of Quaternary frost weathering and erosion. They are scattered in the forest on the top of the hill as well as on its slopes, mostly outside the tourist paths. The best accessible rock formations are north of the top, where also over 5 meters long cave with two entrances can be visited.