Jeziorna hill (285 m) in the northern part of the Kaczawskie Foothills at the outskirts of Nowy Kościół, on the left side of the Kaczawa valley, is in a way special among other basalt hills in the region. The central part of an abandoned quarry was flooded, so that a deep lake originated. Similarly to many other hills, it represents an eroded volcanic cone, built of lava solidified in the former volcanic vent. In the outer parts of the quarry pyroclastic deposits – breccia and tuffs, are also exposed. The quarry itself is approximately 100 x 100 m and the height of its walls reaches 30 m. Basalts show columnar jointing, developed during cooling and shrinking of lava. Immediately above the water surface the columns are seen in cross-section. This allows one to speculate that the axial part of the vent, with columns standing upright, was present in the centre of the excavation area. Probably because of the lake inside the quarry, which has a regular circular outline, Jeziorna is presented as a caldera in some popular publications and guidebooks. This is entirely wrong, as a caldera originates due to collapse of a volcanic cone into the empty magma chamber. Access to the quarry is not signposted, but one can get to the lake using old steps.