From Roman architecture to hilltop castles and fortifications used in defence against the Ottoman empire, Croatia is littered with a rich litany of relics explaining much of the fundamental history of Europe. But, beyond these man-made remnants, Croatia has even more beautiful things to see. Natural locations, shaped by time, evolution and the elements, make up some of Croatia's most spectacular sights. These include river valleys and deltas, subterranean caves, rugged mountain peaks, spectacular waterfalls and areas of such geological importance and biodiversity that they have now been designated as National Parks and UNESCO-protected areas. Here's a slideshow of the best.