English: Croatia's first National park (Plitvice Lake) established in 1949 covers 296.85 km2 of breathtaking natural splendor. The park was inscribed on the UNESCO's World Heritage List in 1979, in recognition of its "outstanding natural beauty and undisturbed production of travertine (tufa) through chemical and biological action". The park represents a phenomenon of karst hydrography. The park harbours a grand collection of waterfalls, gallery of lakes, forest and diversity of animal life. The lakes are renowned for their distinctive colors, ranging from azure to green, grey or blue. The colors change constantly depending on the quantity of minerals or organisms in the water and the angle of sunlight. The sixteen lakes which are formed by natural dams of travertine are separated into upper and lower lakes. About eight km of pathways and wooden walking trails around lakes are accessible to visitors. Trails are descending from an altitude of 636m to 503m above sea level.