The Eye of Earth is a karst spring located in Croatia’s Mount Dinara Nature Park.
The small body of water is the primary source of the Cetina River, which flows from the northwestern slopes of Dinara — 6,000 feet above sea level — down through southern Croatia.
No one knows the precise depth of the cave containing the crystal clear water, but it is suspected to be more than 300 feet deep.
This hidden gem is no easy dive or swim, though, as the water is frigid. Temperatures can go as low as 46.4F even during 95F summers.