Before the Pannonian Sea, the territory of Serbia was covered by the large global ocean of Tethys that separated the two large continents. After strong tectonic movements, the continents began to move closer. Large deformations in the earth's crust caused mountain ranges (Alps, Dinarides ...) to rise from the ocean, and the Tethys Ocean was divided into two sea areas, the Mediterranean (today's Mediterranean Sea) in the south, and the Paratethis Sea, divided into three smaller basins, was formed behind the mountains in the north. Central Paratethys was in today's Central Europe, and its largest basin was the Pannonian, whose southern parts covered parts of Serbia. Climatic changes lead to the melting of continental ice masses. The global sea level dropped and raised even for a few hundred meters. Thus, new continents emerged and shallow seas were formed, such as the Pannonian Sea. By moving the land, the Pannonian Basin finally remained trapped between the mountains. Today’s mountains Fruška Gora, Avala, Povlen, Kosmaj, Cer and Gučevo were at that time islands in the sea that was bustling with life and stretched as far as Kruševac and into the long Great Bay of Morava. In the last collision of the African with the Eurasian continent, Paratethys became smaller and smaller, and in the end it dried up completely.