The Željezničar speleological department was founded at the Mountaineering Society of the same name in 1950. In seventy years of uninterrupted work, more than a thousand speleologists have passed through Željezničar, and on average about fifty of us are active annually – from pupils, students, engineers and doctors of science to pensioners. Some of the members have already specialized, so we have a constant number of speleology instructors, speleo divers, biospeleologists and members of the Croatian Mountain Rescue Service. Our main activity is the exploration of caves and pits throughout the karst areas of Croatia, from Zagorje and Gorski kotar, to Lika and Dalmatia. We are the organizers of the first Croatian speleological expeditions abroad, and we are organizing similar multi-week international research today. In the 1990s, members of Željezničar led expeditions to the deepest pit in Croatia – Luka’s pit on Northern Velebit.