The most important mountain of Zagreb and the oasis of peace for many citizens of Zagreb symbolizing escape from the busy capital, hides a long history. About 12 million years ago, today's form of Medvednica mountain emerged in tectonic processes. It contains all the main types of rocks and fossils from almost all periods in history. The Medvednica mountain is made of a metamorphic green slate that adorns the facades of many buildings in Medvednica such as Tomislav's home and chapel of the Mother of God of the Sljeme Queen of Croats. The second most common rock of Medvednica mountain, characteristic limestone or „litavac“, can be seen at the arcades of Mirogoj and the Zagreb cathedral. An important part of these rocks is the remains of organisms, such as algae and shellfish, who lived in the beaches of the Pannonian Sea that surrounded, and partly covered Medvednica. Unfortunately, limestone from Medvednica mountain is subject to chemical and mechanical wear due to its composition and porous material and is not a viable material, which is why the cathedral is replaced by Italian travertine. Stones of20 Medvednica mountain have been exploited since ancient times, and many abandoned quarries represent a gathering place for many scientists and nature lovers, as numerous fossils and minerals can be found. The remains of different organisms are the indicator of the change of paleoenvironment during the history and complex geological past of Medvednica, which I explained and presented in this work.