Zelenci Nature Reserve, Slovenia

© Andrey Danilovich/Getty Image

A lake that never freezes. Zelenci Nature Reserve, Slovenia

Experience nature's palette at its colorful best at Zelenci Springs, where Italy, Austria, and Slovenia meet, and multiple springs combine to form this aquamarine lake. Here in Slovenia’s Triglav National Park, these crystal-clear waters are the source of the Sava Dolinka, which runs into the country’s longest river, the Sava. Peer closely at the lakebed and you will see tiny springs bubbling up beneath the water's surface. These spring waters never freeze as underground water temperatures stay around 41 degrees Fahrenheit, enough to keep flowing through harsh winters in this alpine region.