Plitvice Lakes National Park (Croatian: Nacionalni park Plitvička jezera, colloquial Plitvice, pronounced [plîtʋitse]) is one of the oldest and the largest national parks in Croatia. In 1979, Plitvice Lakes National Park was added to the UNESCO World Heritage register.The national park is world-famous for its lakes arranged in cascades. Sixteen lakes can be seen from the surface. These lakes are a result of the confluence of several small rivers and subterranean karst rivers. The lakes are all interconnected and follow the water flow. They are separated by natural dams of travertine, which is deposited by the action of moss, algae, and bacteria. The particularly sensitive travertine barriers are the result of an interplay between water, air and plants. The encrusted plants and bacteria accumulate on top of each other, forming travertine barriers which grow at the rate of about 1 cm (0.4 in) per year.