The St. Anna Mountain Geological Reserve was established in 1972 in a part of a former quarry. Legal protection covers limestone in contact with nephelinites. The eastern part of the excavation site reveals limestone from the Triassic. The limestone is of the Karchowice formation which is evident from the discovered S. Silesiacus stems, the multitude of karst Balanoglossites burrows, and the P. Fragilis morphotype which starts appearing only from the Karchowice formation onwards and has bigger shells as well as more articulated ribs than P. Fragilis known from lower formations. Another important feature is the marked presence of the Hexactinellida sponges, the lack of conodonts and the continuation (without angular discrepancy) of the lower shell limestone profile (the highest layers of the Gogoli?skie type from the Dziewkowice formation) in the blocks located just beneath excavated outcrops (50m SE, across the road). Nephelinites are to be found mainly in the deepest western part of the excavation site in the northern wall of the block. Among the many pieces of evidence testifying to hydrothermal changes, of interest is the jasper lens situated within the Karchowice formation close to nephelinites. Among volcanites there are numerous blocks of sandstone, Cenomanian sandstone and Turonian marl limestone. Border lines between these and the volcanites show thermal changes of various intensity. The biggest blocks from the western wal, described before the Second World War, measured a few dozen metres. An elevated rock in the southern part of the block has the best exposed pyroclastic breccias with nephelinite blocks, as well as lapilli and volcanic bombs. The quarry area has undergone a lot of karst phenomena. In addition to the karst changes of the Karachowice limestone, there are also small caves including a corridor of at least 3 metres which is visible in the eastern wall and runs in the E-W direction. Its age is not known, but in other excavation sites there are numerous karst craters which developed on Neogene faults. In the Karachowice limestone, about 15m up the hill, NNE of the corridor outlet, there are remains of the karst crater filled with silt covered in the Cenomanian, which means that there had been a pre-Cenomanian phase of karsting changes. The St. Anna Mountain does not have in situ deposits from the Cretaceous. Total erosion of the Cretaceous layer and a volcanic cone located on it happened after the Oligocene. This means that the present dwarfed shape of St. Anna’s peak composed of volcanites has nothing to do with a genuine volcanic cone but is a monadnock which underwent denudation slower than the limestone surrounding it. Also, the fact that the Cretaceous layer eroded in the Neogene suggests that the highest denudation surface on the Che?m Ridge (385 m) dates back to the Triassic. Great blocks of sedimentary rock which were thermally changed at their meeting point with the volcanites and have been preserved a few dozen metres below the base of the volcano proves that the excavated formation is a remnant of a profoundly eroded nephelinite caldera. This suggests a mixed effusive-eruptive volcanic activity. St. Anna Mountain was a straovolcano. The Che?m range culminates in a volcanic elevation of 400 metres. It has a basalt rock core, an outlet by which magma reached the crater that was probably located near the basilica. Today the area around the basilica still has visible natural outcrops of hardened lava in the form of basalt poles. The volcano was active 27 million years ago. The former crater was probably located a few hundred metres higher than the present peak of the mountain. The height decreased because of natural erosion of rocks. The St. Anna Mountain Geological Reserve of 2.69 ha is located on the south-western slope of the mountain, next to the road to Le?nica. It includes part of an inactive basalt and limestone quarry and provides an interesting illustration of the geological structure of the area. At the bottom of the quarry there are remains of a former volcano crater on the edge of which there are exposed and clearly visible junctions of different types of rocks (both sedimentary and magmatic) as well as basalt poles. Under the influence of molten hot lava, the green tinted sandstone present in the area changed its colour to red. In the vicinity of the reserve there is also a geologically interesting cone of volcanic tuff protected as a monument of nature. This too is a remnant of a volcano eruption. It is composed of erupted ashes and maroon spindle volcanic bombs which are small fragments of lava which had hardened flowing in the air. In addition, the reserve is a site of the protected silver thistle and the common rockrose, a yellow blooming rarity in Opole Silesia. Unfortunately, this reserve of inanimate nature, so unique in this part of the world, is more and more difficult to access each year. This is caused by natural plant succession which covers most of the interesting geological profiles and hides them from the visitors. Therefore, the best time to visit the reserve is early spring when the rock shelves are fully exposed and not yet covered by plants. The reserve is also in danger from the growing illegal garbage dump located nearby, on the northern slopes of the inactive quarry.