Travertines at Spisske Podhradie represent the most extensive travertine complex in Slovakia. The system of travertine structures, so called mounds, emerged in the places where mineral water discharges subsided in the long term – on lineamentals of Hornad Basin flysch subsoil. The oldest one is Drevenik and the castle mound which came to existence at the end of Tertiary period but the most of the structures came from Quaternary period. There are springs that currently create travertine at Siva Brada but the activity of the other mounds´ springs came to an end. An occasional travertine lake in the area known as Pazica is a very interesting phenomenon. On the older travertine mounds there is aesthetically impressive relief developed of separated travertine blocks that tore off and slid down from the corners of the mother massif and create beautiful rock towns (Kamenny Raj, Peklo on Drevenik).