Person preparing to jump into water of Cetina River Spring , also known as Eye Of The Earth, a cold karst spring, Croatia

cetina river spring izvor cetine eye of the earth croatia eye of the earth people picnic tourists swimming summer dragons eye blue hole cetina croatia dalmatia omis cold karst spring karst hydrological system aerial birds eye perspective drone view topdown zoom in push in deep turquoise emerald lake underground drainage visually impressive hidden gem unique shape natural wonder unknown depth ice bath crystal clear groundwater wellspring natural pool phenomenon protected hydrological monument natural marvel sinkhole croatian landscape nature tourism extraordinary shape underground river