Plitvice

Declared in 1949, it is the oldest national park in the Balkans and has been a UNESCO World Heritage Site since 1979. Its 16 stepped lakes, joined by dozens of waterfalls and coloured by dissolved minerals that shift from turquoise to emerald with the light, were formed by the laying down of travertine, a process still going on — so the park's landscape is quite literally still changing shape year by year. During the Croatian war of independence in 1991 it was the setting of the conflict's first armed clashes, which is why it spent a short spell on the List of World Heritage in Danger.