Škocjan Caves are registered in the UNESCO World Heritage Sites. The caves are the largest ever known underground canyon in the world. They represent an example of a contact karst (contact flysch and limestone), with numerous karst phenomena such as sinkholes, natural bridges, ravines, underground canyons, tunnels, springs, etc. They were developed in a small area. Due to the special microclimate condition, an exceptional ecosystem has developed with alternating of the Mediterranean, Submediterranean, Central European, Illyrian and Alpine biogeographical elements. The caves are also included in the list of the world’s most important wetlands (mokrišče) of the Ramsar Convention, as the first underground wetland in the world. They are one of the longest Karst underground wetlands in Europe.