Plitvice Lakes National Park is a special geological and hydrogeological phenomenon. The lakes were declared a national park on April 8, 1949. It is the largest, oldest and most visited Croatian national park. Represents forested mountain area in which there are 16 lakes of various sizes, filled with crystal blue water. Lakes receive water from numerous rivers and streams, and they are connected by cascades and waterfalls. Travertine barriers, which have been made in the period of ten thousand years, are one of the fundamental features of the park. The special geographical location and specific climatic features have contributed to the occurrence of many natural phenomena and rich biodiversity.
The travertine sediments are formed from the Pleistocene to the present in sinkholes and depressions between the surrounding mountains. Upper Lakes in the south predominantly are composed of dolomite and Lower Lakes in the north of the limestone rock. Huge areas of forest, exceptional natural beauty of lakes and waterfalls, flora and fauna, mountain air, contrasting autumn colors, trails and wooden bridges and many more are a part of this unique place which UNESCO pronounced World Natural Heritage in 1979, one of the first in the world. The park is divided into narrower and wider zone according to the degree of protection. It is located in the area of two counties, 91% of the park is in Lika-and 9% in Karlovac County.
The National Park consists of 16 lakes, which are stepwise and descend into each other in a series of 5460 meters air line.The lakes are divided into Upper and Lower lakes.The upper lakes are: Prošćansko, Ciginovac, Okrugljak, Batinovac, Big Lake, Small Lake, Vir, Galovac, Milino, Gradinsko Lake, Big Burget and Kozjak.The lower lakes are: Milanovac, Gavanovac, Kaluđerovac and Novakovic Brod.
Lakes drence waters of Black and White rivers with tributaries and river Rječica and its tributaries. There are many sources where water abundant springs. These are typical karst springs formed on the faults of permeable and impermeable geological formations.
The largest lake is Kozjak with 81.5 hectares, and is the deepest with 47 m. Prošćansko is the second largest and stretches from south to north in the length of 2.5 km.
On the Upper Lakes the geological structure is mainly dolomite, and also on the bottom of the limestone.There are abotu 30 caves. Travertine barriers, that share one reservoir from each other, are of limestone, precipitated from water.Structure of travertine barrier is very sensitive and fragile and requires a high degree of protection. The three main elements are: the abundance of water, tufa and travertine. Without water there would be no lakes nor falls nor lush vegetation. Tufa are plants that produce limestone rocks and change the shape of the lake and lake banks. Travertine barriers are the biological phenomenon of exceptional beauty.
One of the most beautiful waterfalls in Plitvice - Waterfall located between Milanovac and Gavanovca is called the "waterfall Milka Trnina" by Croatian opera prima donna.
Forest and water are mutually connected and one without the second-one can not exist. Forest reserves, preserves and purifies large amounts of water. In the park there is a large area of high-quality woods, including rainforests, which are superior habitat for wildlife. Forest lakes are the habitat of three large European carnivores: brown bear, wolf and lynx. Numerous types of woodpeckers and forest owl testify to the high quality and naturalness of habitats.