The Tarnowskie Góry – Bytom Underground Spaces are the most extensive, special, protected area of natural habitats of the Natura 2000 network. It occupies 3401 hectares. The Underground Spaces comprise coal workings created between Tarnowskie Góry and Bytom from medieval times to the nineteenth century. They are regarded as the second largest overwintering area of bats, which number up to 10 species and several thousands of specimens.