The longest cave yet discovered in the Polish Jura is the Wierna Cave, whose total length of the corridors is more than 1 km. The Wierna Cave is located in Ostrężnik, a small hamlet of the village of Trzebniów, situated within the commune of Niegowa. It was discovered in the early 1990s. Speleologists are delighted with its size and rich cave formations. The Wierna Cave is occasionally accessible to cavers.